Selina Concise Solutions for ICSE Class 9 Geography Chapter 2 Geographic Grid Latitudes and Longitudes

Exercises

I. Short Answer Questions

Question 1. What is a geographic grid ?
Answer: The network of the latitudes and the longitudes is known as a geographical grid.
In simple words: Imagine the Earth wearing a net made of horizontal and vertical lines. This "net" is the geographic grid, and it helps us pinpoint exactly where any place is on the planet.

📝 Teacher's Note: Use a globe with a physical string net over it to show how the lines intersect. This helps students visualize that every point on Earth has a unique "address" in this grid.

🎯 Exam Tip: Use the keyword "network" and mention both "latitudes" and "longitudes" to secure full marks.

Question 2. Who devised the lines of latitude and longitude ?
Answer: Eratosthenes, the Greek philosopher, first time devised the lines of latitude and longitude.
In simple words: A Greek thinker named Eratosthenes was the first person to come up with the clever idea of drawing these lines to map the world.

📝 Teacher's Note: You can mention that Eratosthenes was also the librarian of the Great Library of Alexandria, showing students that great scientific ideas often come from organized study.

🎯 Exam Tip: Remember the name "Eratosthenes." It is a common objective-type question.

Question 3. What are lines of latitude and longitude ?
Answer: The latitudes are the parallel circles with respect to the equator reducing in length northwards and southwards and the poles are the points only. On the other hand longitudes are equal in length drawn from North Pole to South Pole with their intervals reducing towards poles.
In simple words: Latitudes are circles that wrap around the Earth like belts, getting smaller as they move toward the top and bottom. Longitudes are like segments of an orange, going from top to bottom, all the same length but getting closer together at the ends.

📝 Teacher's Note: Use an orange to demonstrate longitudes and a stack of different-sized bangles to demonstrate latitudes. This makes the "reducing length" vs "equal length" distinction clear.

🎯 Exam Tip: Distinguish between them by mentioning that latitudes are "parallel circles" and longitudes are "semicircles of equal length."

Question 4. Mention two characteristics of lines of latitude ?
Answer:
(a) The lines of latitude are parallel to the equator.
(b) The lines of latitude are drawn at an angular distance with respect to the equator.
In simple words: First, they never touch each other (like train tracks). Second, they measure how far north or south you are from the middle of the Earth (the Equator).

📝 Teacher's Note: Explain that "parallel" means the distance between any two lines of latitude is always the same everywhere.

🎯 Exam Tip: The word "parallel" is a keyword. Always mention that they never intersect.

Question 5. Name the two hemispheres of the earth made by the Equator.
Answer: Northern hemisphere and Southern hemisphere.
In simple words: The Equator cuts the Earth into a "top half" (Northern) and a "bottom half" (Southern).

📝 Teacher's Note: Remind students that "hemi" means half and "sphere" means ball. So, a hemisphere is literally half a ball.

🎯 Exam Tip: Be careful with spellings. Ensure you categorize them correctly based on the Equator.

Question 6. Express 1° angular distance in kilometres.
Answer: As the circumference or the equator is nearly about 40,000 km.
So 1° angular distance in km. will be \( 40,000 / 360 = 111\text{ km} \) approximately.
In simple words: If you travel one degree on the Earth's surface, you would have walked about 111 kilometers.

📝 Teacher's Note: Explain that there are 360 degrees in a full circle. By dividing the Earth's total "waistline" by these degrees, we find the size of just one degree slice.

🎯 Exam Tip: Show the calculation \( 40,000 / 360 \) to show how you arrived at the 111 km figure.

Question 7. Name the thermal zones of the earth.
Answer: The thermal zones of the earth are Tropical, Temperate and Polar zones.
In simple words: The Earth is divided into heat zones: the hot middle (Tropical), the mild parts (Temperate), and the freezing ends (Polar).

📝 Teacher's Note: Relate these zones to climate. Tropical = rainforests/deserts; Temperate = four seasons; Polar = ice and snow.

🎯 Exam Tip: You can also use the terms "Torrid", "Temperate", and "Frigid" zones, which are often used interchangeably in textbooks.

Question 8. With the help of degrees, name the important lines of latitude.
Answer:
(a) Tropic of Cancer — \( 23\frac{1}{2}^{\circ}\text{N} \)
(b) Tropic of Capricorn — \( 23\frac{1}{2}^{\circ}\text{S} \).
(c) Arctic Circle — \( 66\frac{1}{2}^{\circ}\text{N} \).
(d) Antarctic Circle — \( 66\frac{1}{2}^{\circ}\text{S} \)
(e) North Pole — \( 90^{\circ}\text{N} \)
(f) South Pole — \( 90^{\circ}\text{S} \)
In simple words: These are the "VIP" lines on the map that mark the boundaries for different climates and the locations of the poles.

📝 Teacher's Note: Help students memorize these by grouping them in pairs (Tropics at 23.5 and Circles at 66.5). The "N" and "S" are vital!

🎯 Exam Tip: Always include the cardinal directions (N/S) next to the degree values. Leaving them out is a common mistake.

Question 9. Which temperature zone receives almost vertical rays of the sun and which zones receive slanting rays ?
Answer: The Tropical zone gets vertical rays of the sun, while temperate and polar zones receive slanting rays of the sun.
In simple words: In the Tropical zone, the sun shines directly from above, making it hot. In other zones, the sun's light hits the ground at an angle, so the heat is spread out and weaker.

📝 Teacher's Note: Use a flashlight to show how a vertical beam is bright and concentrated, while a slanting beam is dimmer and covers a larger area. This explains why the Equator is hotter than the Poles.

🎯 Exam Tip: Use the term "vertical rays" for the Torrid/Tropical zone to indicate maximum heat intensity.

Question 10. Which line is known as the Prime Meridian ? State its importance.
Answer: Greenwich Meridian is called the ‘Prime Meridian’ or the 0° longitude. The time is calculated with respect to this Meridian. So it is the basic Meridian and time is written as G.M.T. (Greenwich Meridian Time) The earth takes 4 minutes for moving 1° distance.
In simple words: The Prime Meridian is the starting line for measuring East and West. It is used to set the world's clock, which is why we call the world standard time GMT.

📝 Teacher's Note: Explain that this line passes through London (Greenwich) because the UK was a global leader in seafaring and mapping when the system was standardized.

🎯 Exam Tip: Mention both its degree (\( 0^{\circ} \)) and its role in time calculation (GMT).

Question 11. How can the general climate of an area be described with the help of the lines of latitudes ?
Answer: The temperature decreases northwards and southwards from the equator. The region within \( 23\frac{1}{2}^{\circ}\text{N} \) and \( 23\frac{1}{2}^{\circ}\text{S} \) will get tropical climate with ample temperature and rainfall. On the other hand the regions between \( 23\frac{1}{2}^{\circ}\text{N} – 66\frac{1}{2}^{\circ}\text{N} \) and \( 23\frac{1}{2}^{\circ}\text{S} – 66\frac{1}{2}^{\circ}\text{S} \) will get temperate climate, while the regions known as Arctic and Antarctic circles get very cold polar climate as Tundra region.
In simple words: The further you move away from the Equator (0°), the colder it gets. We can guess the weather just by looking at a city's latitude!

📝 Teacher's Note: This establishes the link between geometry and geography. Lower latitudes (near 0) are high heat, higher latitudes (near 90) are low heat.

🎯 Exam Tip: Mention specific climate types like "Tropical", "Temperate", and "Polar" for a complete answer.

Question 12. Which line of longitude is used to fix the World Standard Time ? State its value in degrees.
Answer: Greenwich Meridian is used to fix the World Standard Time. Its value in degrees is 0°. This time is written as G.M.T.
In simple words: The 0° line of longitude is the world's master clock. Everything else is measured from here.

📝 Teacher's Note: Reiterate the concept from Q10. This question focuses specifically on its role in timekeeping.

🎯 Exam Tip: Ensure you state the degree value as \( 0^{\circ} \).

Question 13. State the longitudinal value in degrees of Indian Standard Meridian.
Answer: Longitudinal value of Indian Standard Meridian is \( 82\frac{1}{2}^{\circ}\text{E} \). It passes midway through India nearly along the city of Allahabad.
In simple words: India sets its watches by a special line that passes through the middle of the country at \( 82.5^{\circ}\text{E} \).

📝 Teacher's Note: Mention that Allahabad is now officially Prayagraj. This line is chosen because it is roughly in the center of India's east-west width.

🎯 Exam Tip: The value \( 82\frac{1}{2}^{\circ}\text{E} \) is critical for Indian Geography exams.

Question 14. What is meant by IDL ? State its importance.
Answer: IDL means the International Date Line, which is along \( 180^{\circ}\text{E & W} \). The date or day changes while crossing this line i.e. while there is Monday in the Eastern Hemisphere i.e. \( 0^{\circ} – 180^{\circ}\text{E} \), there will be Sunday in the Western Hemisphere i. e. \( 0^{\circ} – 180^{\circ}\text{W} \).
In simple words: The International Date Line is like a magical border on the map. If you step over it going west, you "lose" a day (skip ahead), and if you go east, you "gain" a day (repeat it).

📝 Teacher's Note: Explain that \( 180^{\circ}\text{E} \) and \( 180^{\circ}\text{W} \) are the same exact line. It's the line opposite to the Prime Meridian.

🎯 Exam Tip: Describe what happens to the day/date when crossing the line to explain its "importance."

Question 15. What are the Great Circle Routes ? State their importance.
Answer: The Great Circle Routes follow the great circles i. e. the perimeters of the earth, which cover the shortest distances between any two places in spite of the zigzag routes along the surface of earth. These circles are beneficial for following the shortest distances between any two places and help in saving the time. i. e. the shortest routes are covered in minimum time span.
In simple words: If you want to fly between two cities as fast as possible, you follow a "Great Circle" path. It looks curved on a flat map but it's actually the straightest, shortest way to travel on a round ball.

📝 Teacher's Note: Use a globe and a piece of string. Stretch the string between two far-apart cities. This string shows the Great Circle route. Pilots and sailors use this to save fuel and time.

🎯 Exam Tip: Focus on the phrase "shortest distance between any two places."

Question 16. What is a globe ? State the importance of a globe.
Answer: A globe is a man-made spherical model of the earth. A globe is very useful model to display the actual shape of the earth with its tilted axis ; The rotation and revolution of the earth can be very clearly shown by it along with the continents and oceans.
In simple words: A globe is a tiny Earth. It's better than a flat map because it shows the true shape of our world and how it spins.

📝 Teacher's Note: Remind students that while maps are convenient, they always distort size or shape. A globe is the only way to show Earth without distortion.

🎯 Exam Tip: Mention features like "tilted axis" and "spherical model" when defining a globe.

II. Give reasons for each of the following

Question 1. Lines of latitude carve out the heat zones of the earth.
Answer: The Temperature goes on decreasing from the equator towards the poles. So the latitudinal zones are the actual heat zones of the earth, namely tropical, temperate and polar zones.
In simple words: Because the Sun shines most directly on the Equator, latitudes act as boundaries that divide the Earth into hot, warm, and cold belts.

📝 Teacher's Note: Emphasize that latitude determines the angle of the sun's rays, which is the primary factor for temperature.

🎯 Exam Tip: Linking "latitude" to "angle of sun rays" is the scientific way to explain this reason.

Question 2. Lines of longitude are also called Meridians of longitude?
Answer: The word ‘meridian’ means related to noon or 12 p.m. As every longitude receives the noon time or 12 p.m. at different intervals where the sun’s rays are exactly vertical over a particular longitude. On a particular longitude the noon-time is the same from north to south ; so a longitude is also called a Meridians of longitude.
In simple words: "Meridian" means midday. Because every place on the same longitude line has noon at the exact same moment, we call them meridians.

📝 Teacher's Note: This is why time zones are vertical slices. Everyone in that slice sees the sun reach its highest point at roughly the same time.

🎯 Exam Tip: Explain the Latin root meaning of "meridian" (midday) to show deep understanding.

Question 3. Diametrically opposite lines of longitude and the Equator are called Great Circles.
Answer: Every longitude along with its opposite longitude makes a complete circle around the earth and another complete big circle is the equator; while the latitudes make smaller circles along with the poles to be only points. So the equator and the longitudinal lines around the earth are called the Great Circles.
In simple words: A Great Circle is the biggest possible circle you can draw on a ball. The Equator and pairs of longitude lines (like \( 0^{\circ} \) and \( 180^{\circ} \) together) fit this description perfectly.

📝 Teacher's Note: Visually show that any circle whose center is the center of the Earth is a Great Circle. Small circles (other latitudes) don't pass through the center.

🎯 Exam Tip: Mention that Great Circles divide the Earth into two equal halves (hemispheres).

Question 4. The Greenwich time is called Greenwich Mean Time.
Answer: The time of any place or country is calculated according to the \( 0^{\circ} \) longitude or Greenwich meridian, the time change is of 4 minutes for every \( 1^{\circ} \) longitude. So it is called Greenwich Mean Time.
In simple words: Because the world agreed to use the time in Greenwich as the "average" starting point for everyone's clocks, we call it GMT.

📝 Teacher's Note: The word "Mean" in this context implies a reference or average point used for standardization.

🎯 Exam Tip: Link the term to the \( 0^{\circ} \) longitude and the "standardization of world time."

Question 5. IDL deviates and goes zig-zag near some Islands in the Pacific ocean.
Answer: IDL is not a straight line, but it deviates in order to classify some scattered Islands in a particular divisions of Hemispheres, so that the day and time can be calculated according to the line, as the natural position of the Islands is haphazard.
In simple words: The International Date Line zig-zags to avoid cutting through a country or a group of islands. This way, people living on those islands don't have different days (like Monday and Tuesday) on opposite sides of their town!

📝 Teacher's Note: Mention the Aleutian Islands or Fiji as examples. The "zig-zag" is for human convenience, not geography.

🎯 Exam Tip: State that the deviation is to "avoid confusion of day and date" within a single political territory.

Question 6. A globe is the most popular model of the earth.
Answer: As our earth is spherical in shape, so it can be best represented by a spherical model like a globe. A globe illustrates the position of continents and oceans, the tilted axis of the earth, its rotation, the sea and air routes etc. So a globe is a perfect model of the earth.
In simple words: You can't show a round Earth on a flat piece of paper without squashing things. A globe is round just like the real Earth, making it the most accurate model.

📝 Teacher's Note: Use this to contrast "Globe" vs "Map". Maps have distortions; globes have accuracy in shape, size, and direction.

🎯 Exam Tip: Mention "true representation of shape" as the primary reason.

III. Long Answer Questions

Question 1. Describe the lines of latitude, their importance and use.
Answer: The face of the earth is divided into various parallel circles with respect to the equator on both sides at different angular distances. These lines are very important to decide the climate and temperature range of any place or region as the temperature goes on decreasing from the equator to polewards.
In simple words: Latitudes are horizontal circles that tell us how far North or South a place is. They are useful because they tell us what the climate is like—hot near the middle, cold at the ends.

📝 Teacher's Note: Emphasize that latitudes are imaginary. We can't see them on the ground, but they are essential for science and navigation.

🎯 Exam Tip: In long answers, define them as "parallels" and explain their role in determining "climatic zones."

Question 2. With reference to the International Date Line, state the following:
(a) It is meaning and application.
(b) The important deviations it makes and reasons for the same.
(c) Give an example of how time lost or gained is computed with reference to this line.
Answer:
(a) The time and date changes as we cross the International Date Line i.e. the navigators or pilots have to loose one day while crossing westwards and gain one day while crossing eastwards i.e. When one travels from Tokyo to San Francisco on Monday, he will reach San Francisco on Sunday.
(b) The International Date Line is not a straight line but have some deviations in order to adjust with the pattern of the landforms and some islands to decide for the time and date of these places and regions.
(c) If we are moving from Hawaii Islands towards Shanghai on Tuesday, we will reach there on Wednesday or Thursday probably, but if we are going eastwards from Shangai to Hawaii islands on Tuesday. We may reach there either on Tuesday or Monday.
In simple words: Crossing the IDL is like time travel. Going from the US to Japan makes you jump a day forward. It bends around islands so people there don't get confused about what day it is.

📝 Teacher's Note: Use the "Tokyo to San Francisco" example to explain that even though you fly for hours, you might land at a time *earlier* than when you took off!

🎯 Exam Tip: For (a), clarify the direction of travel (West to East = gain a day; East to West = lose a day).

Question 3. Describe the lines of longitude and state their use in relation to distance and time.
Answer: A longitude is the angular distance of a place east or west of the Prime Meridian or \( 0^{\circ} \) longitude. The lines of longitude are the great semi-circles joining North pole and South pole and are equal in length. These are \( 0^{\circ} – 180^{\circ}\text{E} \) and \( 0^{\circ} – 180^{\circ}\text{W} \) longitudes or total \( 360^{\circ} \). As the earth takes 24 hours to make a complete rotation along its axis crossing \( 360^{\circ} \) lines of longitude, so earth takes nearly 4 minutes to move one degree (\( 1^{\circ} \)) longitude or 111 km length or distance. There is difference of time of one hour between \( 15^{\circ} \) interval of longitudes. According to the clock-time, EGA stands for East-Gain-Add and WLS means West Lose Subtract. In other words for each \( 1^{\circ} \) longitude towards east 4 minutes are to be added and towards west for each \( 1^{\circ} \) longitude 4 minutes are to be subtracted.
In simple words: Longitude lines help us tell time. For every degree you move East, the time goes 4 minutes ahead. For every degree West, it goes 4 minutes back.

📝 Teacher's Note: Teach the mnemonic EGA (East Gain Add) and WLS (West Lose Subtract). It is the simplest way for students to solve time-calculation problems.

🎯 Exam Tip: Remember the math: \( 360^{\circ} = 24\text{ hours} \), therefore \( 15^{\circ} = 1\text{ hour} \), and \( 1^{\circ} = 4\text{ minutes} \).

Question 4. Make a detailed study of finding time with the help of longitudes. Give one practical example.
Answer: Indian Standard Time is based on \( 82\frac{1}{2}^{\circ}\text{E} \) longitude. So if the time in India is 12 noon, so it will be 6.30 A.M. in England or GMT. The time difference between \( 0^{\circ} \) and \( 82\frac{1}{2}^{\circ}\text{E} \) will be \( 82.5 \times 4 = 330\text{ minutes} \) or \( 330 \div 60 = 5\frac{1}{2}\text{ hours} \). So there is difference of \( 5\frac{1}{2} \) hours between India and England, as England lies in the west, so the time will be \( 5\frac{1}{2} \) hours less than India.
In simple words: Because India is East of London, our day starts earlier. When we are eating lunch at 12:00 PM, people in London are just waking up at 6:30 AM!

📝 Teacher's Note: This calculation is why we see "GMT +5:30" on our phones and computers. It's a real-world use of longitude math.

🎯 Exam Tip: Always state whether a place is East or West of the reference point before adding or subtracting time.

IV. Problem Solving

An Example: A cricket match was to be held at Birmingham at 9 a.m. local time. The position of Birmingham is \( 5^{\circ}\text{W} \). Calculate the time the viewers have to tune their television in Sydney \( 151^{\circ}\text{E} \).
Answer:
The local time at Birmingham is 9 am.
The location of Birmingham is \( 5^{\circ}\text{W} \) of Prime Meridian.
The GMT would be 9:20 a.m. [\( 9.00\text{hrs} + (5^{\circ} \times 4\text{min}) = 9.00\text{hrs} + 20\text{ min} = 9.20\text{ a.m.} \)]
Sydney is located at \( 151^{\circ}\text{E} \) of Prime Meridian.
At any point of time Sydney would be \( 151 \times 4 = 604\text{ min} = 10\text{ hrs 4 min} \) ahead of GMT.
When it is 9:20 a.m. GMT the local time at Sydney would be \( (9:20 + 10:04) = 19:24\text{ hrs} \) or 7:24 p.m.
In order to watch the Birmingham match at Sydney the viewers would have to tune their televisions at 7:24 p.m. local time.
In simple words: Because Sydney is far to the East of England, their clocks are over 10 hours ahead. A morning match in England happens in the evening for people in Australia.

📝 Teacher's Note: Break this into two steps for students: First find GMT, then find the target city's time. This "stop-over at GMT" method prevents calculation errors.

🎯 Exam Tip: Pay close attention to a.m. and p.m. transitions when adding many hours.

Question 1. An important programme was to be broadcast from Mumbai at 7.30 p.m. This was heard by some Indian sailors near Ivory Coast in West Africa at \( 20^{\circ}\text{W} \) longitude. What was the local time there ?
Answer: According to the Indian Standard Time 7.30 p.m. based on \( 82\frac{1}{2}^{\circ}\text{E} \) longitude was the time at Mumbai. The longitudinal difference between Mumbai (IST) and Ivory Coast at \( 20^{\circ}\text{W} \) is \( 82.5 + 20 = 102.5^{\circ} \). So \( 102.5 \times 4 = 410.0\text{ minutes} = 6\text{ hours 50 minutes} \), i.e. the time will be 6 hours 50 minutes less than 7.30 p.m. So the time will be 12.40 p.m.
In simple words: West Africa is many degrees West of India, so their time is "behind." When it's evening in Mumbai, it's just past lunchtime on the Ivory Coast.

📝 Teacher's Note: When one longitude is East and the other is West, you must **ADD** the values to find the total distance between them.

Question 2. What is the longitude of a place where the local time 1:15 p.m. when it is 4 a.m. at Chicago (\( 88^{\circ}\text{W} \)) ?
Answer: The time difference between the two places is 9 hours and 15 minutes or \( 540 + 15 = 555\text{ minutes} \). So the longitudinal difference will be \( 555 / 4 = 138.75^{\circ} \). So the longitude of the required place will be \( 50^{\circ}45^{\prime}\text{E} \) i.e. it will cover \( 88^{\circ} \) from west to \( 0^{\circ} \) and \( 50^{\circ}45^{\prime} \) east from \( 0^{\circ} \) or Greenwich line.
In simple words: Since the time is much later than Chicago, the place must be far to the East. We calculated the distance and found it is halfway across the world from Chicago.

📝 Teacher's Note: \( 0.75 \) of a degree is \( 45 \) minutes (\( 0.75 \times 60 = 45 \)). Always convert decimals to degrees and minutes in the final answer.

Question 3. Calculate the time at Durban (longitude \( 30^{\circ}\text{E} \)) when the time is 7.00 a.m. at New York (\( 75^{\circ}\text{W} \)).
Answer: The longitudinal difference between Durban and New York is \( 30^{\circ} + 75^{\circ} = 105^{\circ} \), so the time will be \( 105 \times 4 = 420\text{ minutes} \) ahead from New York. There is the difference of 420 minutes or 7 hours, or 2 p.m.
In simple words: New York is West and Durban is East. We add their longitudes to get \( 105^{\circ} \). Converting this to time gives us 7 hours. Adding 7 hours to 7 a.m. gives us 2 p.m.

Question 4. Calculate the longitude of a place where the local time is 6.00 a.m., when the time is 9.00 p.m. at New Delhi on longitude \( 77^{\circ}\text{E} \).
Answer: The time difference between the required place and New Delhi is \( 6 + 9 = 15\text{ hours} \), so the time in minutes \( = 15 \times 60 = 900\text{ minutes} \). So the longitudinal difference \( = 900 / 4 = 225^{\circ} \). So the place will be in the west \( 225^{\circ} – 77^{\circ} = 148^{\circ}\text{W} \).
In simple words: The time is 15 hours behind New Delhi, so the place is very far West. We found the longitude is \( 148^{\circ}\text{W} \).

Question 5. Calculate the local time at Singapore (\( 104^{\circ}\text{E} \)) when it is 6.00 p.m. at Greenwich.
Answer: The longitudinal difference at Singapore and Greenwich is \( 104^{\circ} \), so the time difference is \( 104 \times 4 = 416\text{ minutes} \) i.e. 6 hours 56 minutes. So the time at Singapore will be 12.56 a.m.
In simple words: Singapore is almost 7 hours ahead of London. If it's evening in London, it's already the middle of the night in Singapore.

Question 6. Calculate the location of a place where the local time is noon when it is 7.30 p.m. at Greenwich.
Answer: Time difference is \( 12 – 7.30 = 4.30 \) or 4 hours 30 minutes \( = 240 + 30 = 270\text{ minutes} \). So the longitudinal difference is \( 270 / 4 = 67.5^{\circ} \). So the longitude is \( 67.5^{\circ}\text{W} \) or \( 67\frac{1}{2}^{\circ}\text{W} \).
In simple words: The place is 4.5 hours behind London, so it must be to the West. The math shows it is at \( 67.5^{\circ}\text{W} \).

Question 7. What is the time and day at Mumbai (\( 73^{\circ}\text{E} \)) when it is Sunday 10.30 p.m. at Shillong (\( 92^{\circ}\text{E} \)) ?
Answer: The longitudinal difference is \( 92^{\circ} – 73^{\circ} = 19^{\circ} \). So the time difference is \( 19 \times 4 = 76\text{ minutes} \) or 1 hour 16 minutes. Since Mumbai is West of Shillong, we subtract the time. The time at Mumbai is 9.14 p.m.
In simple words: Both cities are in India, but the Sun hits Shillong first because it's further East. Mumbai's "true" sun-time is about an hour behind Shillong's.

Practice Questions (Solved)

Question 1. How many lines of latitude are there ?
Answer: \( 180 + 1 = 181 \)
In simple words: There are 90 lines going up to the North Pole, 90 going down to the South Pole, and 1 extra for the Equator in the middle.

Question 2. How many lines of longitude are there ?
Answer: \( 360 – 1 = 359 \). (Note: Usually counted as 360 including the overlap of 180 E/W).
In simple words: Just like a circle has 360 degrees, there are 360 lines of longitude wrapping around the Earth.

Question 3. Which meridian is called Prime meridian ?
Answer: \( 0^{\circ} \) meridian.
In simple words: The "Number Zero" line of longitude.

Question 4. What is the latitude of equator ?
Answer: \( 0^{\circ} \)
In simple words: The starting point for measuring North and South.

Question 5. What is the latitude of Tropic of Cancer ?
Answer: \( 23\frac{1}{2}^{\circ} \) North.
In simple words: The hot northern boundary.

Question 6. What is the latitude of Tropic of Capricorn ?
Answer: \( 23\frac{1}{2}^{\circ} \) South.
In simple words: The hot southern boundary.

Question 7. Which is the longest line of latitude ?
Answer: Equator.
In simple words: Because the Earth is fattest in the middle, the Equator is the biggest circle.

Question 8. Which star is located vertically above the North pole ?
Answer: Pole-Star.
In simple words: The North Star (Polaris) sits right above the top of the Earth's axis.

Question 9. Into how many time zones, has the world been divided?
Answer: 24
In simple words: One zone for every hour of the day.

Question 10. What do you mean by meridians ?
Answer: Lines of longitude.
In simple words: Another name for the vertical lines on a map.

Question 11. What is the relation between Temperature and Latitude of a place ?
Answer: The temperature decreases with latitude.
In simple words: As the latitude number goes up (moving away from 0°), the weather gets colder.

Question 12. What is latitude of North pole and South pole ?
Answer: \( 90^{\circ}\text{N} \) and \( 90^{\circ}\text{S} \).
In simple words: The absolute top and bottom points of the Earth.

Question 13. Why are there 180 parallels of latitude ?
Answer: Because North pole to South pole (a hemisphere) has an angle of \( 180^{\circ} \).
In simple words: If you slice a ball from top to bottom, the curve makes a half-circle of 180 degrees.

Question 14. Name the two hemispheres of the Earth made by the equator ?
Answer: Northern Hemisphere and Southern Hemisphere.
In simple words: Top half and bottom half.

Question 15. Which temperature zone receives slanting rays ?
Answer: Polar Zone.
In simple words: The icy ends of the Earth where the sun never shines directly from above.

Question 16. Name the two reference lines with respect to which the distances of various places on the earth’s surface are measured ?
Answer: Prime Meridian and Equator.
In simple words: These are the "Starting Lines" for the whole world's map.

Question 17. What is the rate of change of time per degree of longitude ?
Answer: 4 minutes per degree.
In simple words: As the Earth spins, it takes 4 minutes for one degree line to move past the Sun.

Question 18. Why are the letters N or S added to latitude values ?
Answer: The latitudes in Northern Hemisphere are marked N while the latitude in Southern Hemisphere marked S.
In simple words: We need to know if you are going North toward the Arctic or South toward Antarctica!

Question 19. Why are letters E or W added to longitude values ?
Answer: The longitudes in the Eastern Hemisphere are marked E while the longitudes in the Western Hemisphere are marked W.
In simple words: This tells us if a place is to the East or West of London.

Question 20. What is the importance of Tropic of Capricorn ?
Answer: It marks the Southern limit of tropical zone.
In simple words: It's the "border line" in the South. Beyond this line, the Sun never shines directly overhead.

Question 21. What is meant by “the Parallels of Latitude ?
Answer: If you examine a globe or map, you will see two sets of lines drawn across it. One set of lines runs north and south of Equator and Parallel to it. These lines are called Parallels of a Latitude. The total number of such lines, if drawn at a distance of one degree, from one another is 180 : 90 North of the equator and 90 South of the equator.
In simple words: They are circles that stay exactly the same distance apart all the way around the Earth.

Question 22.
(a) What do you mean by Longitude of a place ? How is longitude of a place determined ?
(b) What is the “Prime Meridian” ?
(c) What is the difference between Prime Meridian and other meridians of longitude ?
(d) Explain how latitudes and longitudes help to determine the position of a place on the globe ?
(e) Explain how the longitude of a place affects the time.
Answer:
(a) Longitude is the distance of a place east and west of the Prime Meridian along a parallel of latitude. This distance is measured in degrees. For example, if Delhi is \( 77^{\circ}\text{E} \), it means it is \( 77^{\circ} \) East of London. Longitude can be determined by comparing Local Time with Greenwich Time using a Chronometer (a very accurate clock). If it's 2 p.m. in London and 5 p.m. somewhere else, that place is 3 hours (\( 180\text{ minutes} \)) ahead, meaning it is \( 180 / 4 = 45^{\circ}\text{E} \).
(b) The Prime Meridian is the \( 0^{\circ} \) longitude line that passes through Greenwich, London. It is the starting point for measuring East and West.
(c) The Prime Meridian is the reference line (\( 0^{\circ} \)). All other meridians show the distance from this line and are marked East or West.
(d) They work like coordinates in a game. Where a latitude line and a longitude line cross, that is the exact spot of a city. For example, London is at \( 51^{\circ}30^{\prime}\text{N} \) and \( 0.5^{\circ}\text{W} \).
(e) As the Earth rotates from West to East, the Sun appears to move West. The Earth covers \( 360^{\circ} \) in 24 hours, which means \( 1^{\circ} = 4\text{ minutes} \). Places to the East gain time (add), and places to the West lose time (subtract).
In simple words: Longitudes are time-markers. Using a very accurate watch and comparing your "noon" with London's "noon," you can figure out exactly where you are in the world.

📝 Teacher's Note: The Chronometer was a life-saving invention for sailors. Before it, they could find their latitude easily using stars, but finding longitude was almost impossible!

Question 23.
(a) What is “Greenwich Mean Time” ?
(b) How far is it correct to say that local time is the Sun time ?
(c) How can you say that the use of ‘Local Time’ is very inconvenient nowadays in practical life ?
(d) Why do some countries have many time zones ?
Answer:
(a) GMT is the time based on the \( 0^{\circ} \) longitude at Greenwich. It is the universal standard used by all countries.
(b) It is correct because "noon" is defined as the moment the Sun is at its highest point in your sky. This is literally "Sun time."
(c) It's inconvenient because every city would have a slightly different time. If you took a short train ride, you'd have to change your watch by a few minutes every time! We use Standard Time to keep a whole country on the same clock.
(d) Very wide countries like Russia, Canada, and the USA have many time zones because they are so huge that when the Sun is rising on one side, it is already midday on the other. Russia once had 11 time zones!
In simple words: We need standard time so we don't have to keep changing our watches every time we drive to a new city. Big countries need many zones so that "noon" actually feels like the middle of the day for everyone.

📝 Teacher's Note: Use the example of a 19th-century train station. Before standard time, every station had a different clock based on the local sun, making it impossible to write a useful timetable.

Question 24. Give reasons for the following :
(a) There are no latitudes higher than \( 90^{\circ}\text{N} \) and \( 90^{\circ}\text{S} \).
(b) The opposite meridians of longitude form a Great Circle.
(c) Local time is a theoretical reality, while Standard Time is a practical necessity.
(d) “The International Date Line is not a straight line coinciding with longitude 180 degrees.” Why ?
(e) The distance between two consecutive meridian, is equal to about 111 kilometres only at the equator.
(f) When it is noon at Cairo (\( 30^{\circ}\text{E} \)), the local time in New York (\( 75^{\circ}\text{W} \)) is 5.00 a.m.
(g) All parallel other than equator are not Great Circles.
(h) A person, travelling from Mumbai to London, alters the time on his watch at several places.
Answer:
(a) Because the distance from the Equator to a Pole is exactly one-fourth of a circle (\( 360 / 4 = 90^{\circ} \)). You can't go further than the top or bottom of the ball.
(b) Two opposite semi-circles combined (\( 0^{\circ} + 180^{\circ} \)) make a full circle that passes through the center of the Earth.
(c) Local time changes every mile you walk, which is confusing. Standard time keeps a whole region uniform for travel and business.
(d) To avoid cutting through islands and landmasses, so a single country can have the same date everywhere.
(e) Because longitudes converge (meet) at the poles. They are widest apart at the Equator and touch each other at the top and bottom.
(f) Cairo is \( 30^{\circ}\text{E} \), New York is \( 75^{\circ}\text{W} \). Total distance = \( 105^{\circ} \). Time difference = \( 105 \times 4 = 420\text{ minutes} = 7\text{ hours} \). New York is West, so we subtract 7 hours from 12 noon = 5:00 a.m.
(g) Other latitudes are smaller circles and their centers are not the center of the Earth.
(h) Because the person is crossing many different time zones (longitudes) during the flight.
In simple words: These are the "whys" of geography. Longitudes get skinnier at the poles, and New York is 7 hours behind Cairo because it's further West on the spinning Earth.

📝 Teacher's Note: For (f), show the subtraction clearly: \( 12\text{ (noon)} - 7\text{ hours} = 5\text{ a.m.} \). For (h), mention that the pilot usually announces when you enter a new zone.

Question 25. What do you mean by the Latitude of place ?
Answer: Latitude is the distance of a place north or south of the equator along a meridian. This distance is measured in degree. When we say that the Latitude of Delhi is \( 28\frac{1}{2}^{\circ} \) North, we mean that Delhi lies North of the equator.
In simple words: Latitude tells you how far up or down the Earth you are from the middle "waistline" (the Equator).

Question 26. How are Latitudes measured ?
Answer: The latitude of a place is the angular distance of the point north or south of the equator measured in degrees. The equator is taken as \( 0^{\circ} \) latitude. Latitudes are measured from \( 0^{\circ} \) to \( 90^{\circ}\text{N} \) and \( 0^{\circ} \) to \( 90^{\circ}\text{S} \). One degree of latitude is equivalent to the length of about 111 km or 69 miles.
In simple words: We measure them in degrees starting from the middle (0°) and going up or down to 90°.

Question 27. Explain why the lines of longitude are called meridians of longitude ?
Answer: Lines of longitude are called Meridians because all places along a lines of longitude experience mid-day at the same time. They are semi-circles of equal length joining the North and South poles.
In simple words: If you and a friend are on the same longitude line, the Sun will be at its highest point for both of you at the exact same moment.

Question 28. State two properties of lines of latitude.
Answer:
1. The length of the lines of latitudes decrease with distance from the equator.
2. All lines of latitude are circles parallel to the equator.
In simple words: They are perfect circles that never touch and get smaller as you get closer to the poles.

Question 29. State two properties of lines of longitude.
Answer:
1. The distance between two consecutive longitude decreases gradually with distance from the equator.
2. All lines of longitude are semicircles of equal length.
In simple words: They all have the same length, but they bunch up and touch at the poles.

Question 30. Clearly distinguish Longitude from Lines of Longitude.
Answer: Longitude is the distance of a place from the Prime Meridian while lines of longitude are lines drawn on a map or globe showing the longitude of all the places at the distance from the Prime Meridian. These lines join the north and south poles and cut the Equator at right angles.
In simple words: Longitude is the "measurement" (like 77 degrees), while the Line of Longitude is the actual "drawing" on the map.

Question 31. What do you mean by “Meridians or Lines of Longitude” ?
Answer: The other set of lines join the north and south poles and cuts the equator at right angles. These lines are called Lines of Longitude or Meridians. The total number of such lines, if drawn \( 1^{\circ} \) apart, is 360° – 180° East and 180° West of the Prime Meridian. It should be noted that 180° East and 180° West in the same lines.
In simple words: These are the vertical lines from pole to pole. There are 360 of them in total around the world.

Question 32. What is the latitude of :
1. Equator
2. North Pole
3. South Pole
4. Tropic of Cancer
5. Tropic of Capricorn
6. Arctic Circle
7. Antarctic circle ? Also give their characteristics.
Answer:
1. Equator (\( 0^{\circ} \)): Days and nights are equal throughout the year. Sun rays fall vertically on March 21 and Sept 23.
2. North Pole (\( 90^{\circ}\text{N} \)): Days and nights are of six-months duration.
3. South Pole (\( 90^{\circ}\text{S} \)): Also has six-month long days and nights.
4. Tropic of Cancer (\( 23\frac{1}{2}^{\circ}\text{N} \)): Vertical sun rays fall here on June 21.
5. Tropic of Capricorn (\( 23\frac{1}{2}^{\circ}\text{S} \)): Vertical sun rays fall here on December 22.
6. Arctic Circle (\( 66\frac{1}{2}^{\circ}\text{N} \)): Has 24 hours of daylight on June 21 and 24 hours of night on Dec 22.
7. Antarctic Circle (\( 66\frac{1}{2}^{\circ}\text{S} \)): Has 24 hours of daylight on Dec 22 and 24 hours of night on June 21.
In simple words: These lines mark special sun behaviors. At the poles, the sun doesn't set for half the year! At the tropics, the sun is perfectly overhead once a year.

📝 Teacher's Note: These dates mark the "Solstices" and "Equinoxes." It's a great way to link geography to the seasons.

Question 33. What adjustment has to be made when ships cross the International Date Line ? OR Explain why a day appears to be lost in sailing round the world from east to west and gained when travelling from west to east.
Answer: The earth rotates from west to east, so eastern places see the sunrise first. If you travel West (following the sun), you set your watch back 4 minutes for every degree. After \( 360^{\circ} \), you have set your watch back 24 hours total. This makes it look like you "lost" a day. Francis Drake once thought it was Saturday when it was actually Sunday because of this! Conversely, travelling East, you put your watch forward and eventually "gain" a day.
In simple words: When you fly West, you are "chasing" the sun, so you keep making your day longer. By the time you go around the world, you've added up enough extra time to lose a whole calendar day.

Question 34. Define Equator. What is its main function ?
Answer: Equator is the parallel of zero degree latitude. It is an imaginary circle round the Earth bisecting it into halves i.e. Northern Hemisphere and Southern Hemisphere. It serves as reference line for the location of different places on the earth.
In simple words: It's the Earth's "waistline" and the starting line for measuring North and South.

Question 35. What will be local time at Delhi \( 77^{\circ}\text{E} \) longitude when is 3 p.m. at Tokyo \( 139^{\circ}\text{E} \) longitude ?
Answer:
Difference in longitude \( = 139^{\circ} - 77^{\circ} = 62^{\circ} \).
Time difference \( = 62 \times 4 = 248\text{ minutes} = 4\text{ hours 8 minutes} \).
Delhi is West of Tokyo, so we subtract: \( 3:00\text{ p.m.} - 4\text{ hrs 8 min} = 10:52\text{ a.m.} \)
In simple words: Tokyo's clocks are about 4 hours ahead of Delhi. When people in Tokyo are starting their afternoon tea, people in Delhi are still finishing their breakfast.

Question 36. What will be the local time at Madras \( 80^{\circ}\text{E} \) ? When it is 9 P.M. at New York \( 74^{\circ}\text{W} \) ?
Answer:
Longitude difference \( = 80^{\circ} + 74^{\circ} = 154^{\circ} \).
Time difference \( = 154 \times 4 = 616\text{ minutes} = 10\text{ hours 16 minutes} \).
Madras is East of New York, so we add 10 hours 16 minutes to 9 p.m.
The time at Madras will be 7:16 A.M. next morning.
In simple words: Madras is way to the East of New York. When New Yorkers are going to sleep at night, people in Madras are just starting their next morning.

Question 37. “The degree of longitude decreases in length poleward”. Why?
Answer: Equator is the longest parallel on the Earth. All other parallels become shorter polewards due to spherical shape of the Earth. So the meridians near the poles have a narrow space. One degree of longitude is the longest at the equator (111 km) at 45° latitude it is 79 km, at 60° latitude it is 55 km and at poles, it is zero km.
In simple words: Imagine an orange. The gaps between the peel segments are widest in the middle but they all meet at a point at the top and bottom.

📝 Teacher's Note: This is why the "grid squares" on a map near Greenland look much skinnier than the grid squares near Brazil.

Question 38. What is the relation between longitude and time ? Or “There is a difference of 4 minutes of time for one degree of longitude”. Why ?
Answer: There is a close relation between longitude and time. The Earth makes one complete rotation of \( 360^{\circ} \) in 24 hours. It passes through \( 15^{\circ} \) in one hour or one degree in four minutes. As the Earth moves from West to East, the places East of Greenwich gain time whereas the places West of Greenwich loose time.
In simple words: The Earth is like a big clock. Since it takes 24 hours to do a full spin, each small "slice" of a degree represents 4 minutes of that spin.

Question 39. “Lines of latitude are called parallels of latitude” Why?
Answer: Lines of latitudes join the places of same latitude. These are circles drawn round the earth, parallel to the equator. Therefore, these are called parallels of latitude.
In simple words: Just like two lines of a notebook that never cross, these circles wrap around the Earth and always stay the same distance apart from each other.

Question 40. A ship crossing international date line at mid-night on Wednesday Eastwards, find that it is mid-night Tuesday on American side. Why ?
Answer: A ship crossing international date line from West to East gains a day. It repeats a day. A day is subtracted from the calendar. So when it is Wednesday mid-night on Asiatic side, it is Tuesday midnight on the American side.
In simple words: When you go from Asia to America across the IDL, you "go back in time" by one day. You get to live Tuesday all over again!

Question 41. Mid-days Sun can be seen overhead in Chennai twice a year, but not even once in Delhi. Why ?
Answer: Tropic of Cancer is the Northernmost limit of overhead Sun. Sun’s rays do not fall vertical beyond \( 23\frac{1}{2}^{\circ}\text{N} \) latitude. Delhi is located North of Tropic of Cancer, so the Sun is never overhead at Delhi. But Chennai has overhead Sun twice a year:
1. When the Sun moves northward, from equator to Tropic of Cancer.
2. When the Sun shifts from Tropic of Cancer back to equator.
In simple words: The Sun only shines perfectly straight down between the Tropics. Chennai is inside this zone, so the Sun hits the top of your head twice a year. Delhi is too far North, so the Sun is always slightly tilted there.

📝 Teacher's Note: This is a very popular logic question. Just remember: Outside the Tropics (Cancer to Capricorn), the sun is never directly at 90 degrees.

Question 42. Explain why there is no higher latitude other than \( 90^{\circ}\text{N} \) and \( 90^{\circ}\text{S} \).
Answer: Latitude is the angular distance from the plane of the equator. All surfaces (planes) or circles make a maximum angle of \( 90^{\circ} \) from the plane of the equator. Therefore, maximum latitude is \( 90^{\circ}\text{N} \) in the Northern Hemisphere and \( 90^{\circ}\text{S} \) in the Southern Hemisphere.
In simple words: If you start at the middle and go straight up, you turn 90 degrees to reach the very top. You can't turn more than that without starting to go down the other side!

Question 43. Name the five important parallels of latitude.
Answer:
(a) Equator — \( 0^{\circ} \)
(b) Tropic of Cancer – \( 23\frac{1}{2}^{\circ} \) North parallel.
(c) Tropic of Capricorn – \( 23\frac{1}{2}^{\circ} \) South parallel.
(d) Arctic circle – \( 66\frac{1}{2}^{\circ} \) North parallel.
(e) Antarctic circle – \( 66\frac{1}{2}^{\circ} \) South parallel.
In simple words: These are the five main lines that divide our Earth into climate zones.

Question 44.
(a) What do you mean by local time ?
(b) What is the local time when it is noon at a place ?
(c) What are the main characteristics of local time ?
Answer:
(a) Local time : The local time of a place is the time of its own meridian. It is calculated by the position of the Sun.
(b) It is 12 o’clock. All the watches of that place should be set according to that time.
(c) Characteristics :
1. Every meridian has a different local time.
2. The places on the same meridian have the same local time.
3. The Eastern places will be ahead of Western places for local time.
4. Sundial was a simple and old method to determine local time.
In simple words: Local time is "Sun time." If the sun is at its highest point right above you, it's 12:00 PM local time.

Question 45.
(a) What is the rule of changing the date while crossing the international date line ?
(b) What is meant by ‘six-day week’ and ‘eight-day week’?
Answer:
(a) Westward travel (USA to Japan): A day must be added. When crossing, you "miss" a day from the calendar. If you cross on Monday, the next day is Wednesday. This results in a "six-day week."
(b) Eastward travel (Japan to USA): A day must be subtracted. When crossing, you "gain" a day. It repeats a day. If you cross on Monday, the next day is Monday again. This results in an "eight-day week."
In simple words: Traveling West makes you skip a day, so your week feels short (6 days). Traveling East makes you repeat a day, so your week feels extra long (8 days).

📝 Teacher's Note: This is often the most confusing part of the chapter. Use a desk calendar and move a toy plane over a line to show the "jumping" of dates.

🎯 Exam Tip: Use the specific terms "Six-day week" and "Eight-day week" to score high on logic-based travel questions.