CBSE Class 6 Science Measurement of Length, Mass and Time Worksheet Set 01

Answer: A cubit is the length from the elbow to the tip of the middle finger, and it differs from person to person. A unit that changes with the person gives different results each time, so it cannot be standard.

Teacher's Note:
1. Different people have different arm lengths.
2. A standard unit must have the same value for everyone.

Answer: A standard unit has a fixed value accepted everywhere. It lets people measure, compare and communicate lengths, masses and times without confusion.

Teacher's Note:
1. Without a common unit, two people would get different results for the same object.
2. Standard units also make trade and science reliable.

Answer: Two examples are measuring the length of a pencil or cloth with a scale, and finding the mass of vegetables on a weighing balance. Reading the time on a clock is another example.

Teacher's Note:
1. Measurement means comparing a quantity with a standard unit.
2. Shopping, cooking and travel all depend on measurement.

Answer: The shopkeeper measures the mass of the rice, usually in kilograms.

Teacher's Note:
1. Rice is sold by mass and not by length.
2. A weighing balance is the instrument used.

Answer: (d) metre. The metre is the SI unit of length; the others are smaller units obtained from it.

Teacher's Note:
1. Centimetre, decimetre and millimetre are parts of a metre.
2. The symbol for metre is m.

Answer: (b) kilogram. The kilogram is the SI unit of mass.

Teacher's Note:
1. A gram is one-thousandth of a kilogram.
2. The symbol for kilogram is kg.

Answer: (d) second. The second is the SI unit of time.

Teacher's Note:
1. Hours and minutes are larger units made from seconds.
2. The symbol for second is s.

Answer: The kilometre (km) is used because the distance is very large.

Teacher's Note:
1. Long distances are expressed in kilometres to keep the numbers small.
2. Using metres would give a very large number.

Answer: The millimetre (mm) is suitable because a coin is very thin.

Teacher's Note:
1. Small lengths are measured in small units.
2. A centimetre would be too large for this measurement.

Answer: 1. Symbols are written in small letters, such as m, kg and s, except those named after a person.
2. No full stop is placed after a symbol.
3. The symbol is the same for singular and plural (5 m, not 5 ms).
4. A space is left between the number and the symbol (3 kg).

Teacher's Note:
1. The rules keep symbols uniform across the world.
2. Writing 'cm.' or '5 kgs' is therefore incorrect.

Answer: (a) 1 km = 1000 m, so 3.5 km = 3.5 × 1000 = 3500 m.
(b) 2500 m = 2500 ÷ 1000 = 2.5 km.

Teacher's Note:
1. Multiply when changing to a smaller unit and divide when changing to a larger unit.
2. Remember that 1 km equals 1000 m.

Answer: Press together a stack of, say, 100 sheets and measure the thickness of the stack with a scale. Divide the thickness by 100 to get the thickness of one sheet.

Teacher's Note:
1. One sheet is too thin to measure directly.
2. Measuring many sheets and dividing reduces the error.

Answer: A flexible measuring tape is used, because the chest is curved and a rigid scale cannot follow it.

Teacher's Note:
1. The tape bends along the body.
2. Tailors use the same kind of tape.

Answer: 1. Place the scale along the length with the zero mark (or a whole-number mark if the end is worn) exactly at one end of the object.
2. Keep the eye directly above the mark being read, so that the reading is not wrong due to a slanting view.

Teacher's Note:
1. Reading from a side angle gives a wrong value.
2. A broken end of the scale should never be used as zero.

Answer: Lay a thread carefully along the curved line, mark its start and end on the thread, then straighten the thread and measure the marked length on a scale.

Teacher's Note:
1. A straight scale cannot follow a curve.
2. A thread bends along the line and can then be made straight.

Answer: Millimetre < centimetre < metre < kilometre. (1 mm = 0.1 cm, 1 cm = 0.01 m, 1 km = 1000 m.)

Teacher's Note:
1. Convert all to the same unit before comparing.
2. This order runs from the smallest to the largest unit.

Answer: Area = length × breadth = 50 × 35 = 1750 m².
In hectares: 1750 ÷ 10 000 = 0.175 hectare.

Teacher's Note:
1. Area is in square units.
2. A hectare is used for large fields.

Answer: Breadth = area ÷ length = 450 ÷ 25 = 18 cm.

Teacher's Note:
1. Area = length × breadth, so breadth = area ÷ length.
2. The answer is in cm because the area is in cm² and the length in cm.

Answer: Length = area ÷ breadth = 600 ÷ 15 = 40 m.

Teacher's Note:
1. Divide the area by the known side.
2. Check: 40 × 15 = 600.

Answer: 1 m = 10 dm, so 1 m² = 10 dm × 10 dm = 100 dm².

Teacher's Note:
1. Squaring the length factor gives the area factor.
2. 1 m² therefore equals 100 dm².

Answer: Mass is the amount of matter contained in an object. Its SI unit is the kilogram (kg).

Teacher's Note:
1. Mass does not change from place to place.
2. It is measured with a balance.

Answer: Area = ½ × base × height = ½ × 10 × 5 = 25 cm².

Teacher's Note:
1. The area of a triangle is half of base times height.
2. The unit is cm² because it is an area.

Answer: Volume = 50 × 40 × 10 = 20 000 cm³, so mass = 20 000 g = 20 kg.

Teacher's Note:
1. Each cm³ of water has mass 1 g.
2. Divide by 1000 to change grams to kilograms.

Answer: Number of biscuits = 10 × 50 = 500. Mass of one biscuit = 5000 g ÷ 500 = 10 g.

Teacher's Note:
1. Convert kilograms to grams first.
2. Then divide by the total number of biscuits.

Answer: 7.40 kg = 7400 g. Mass of one sweet = 7400 ÷ 110 = 67.27 g, which is about 67 g.

Teacher's Note:
1. Convert to grams before dividing.
2. The answer is rounded to the nearest gram.

Answer: 1 metric tonne = 1000 kg = 10 quintals (1 quintal = 100 kg).

Teacher's Note:
1. A tonne is used for very heavy loads.
2. A quintal is used for grains.

Answer: Events that repeat after equal intervals of time are periodic events. Examples are the swing of a pendulum and the rising of the Sun every day.

Teacher's Note:
1. Their repetition can be used to measure time.
2. Early clocks used such events.

Answer: Two ancient time-measuring devices are the sundial and the water clock (clepsydra). The sand clock (hourglass) is another.

Teacher's Note:
1. Sundials use the Sun's shadow.
2. Water and sand clocks use steady flow.

Answer: A stopwatch is used, as it can measure very short intervals accurately.

Teacher's Note:
1. It can be started and stopped at will.
2. Many stopwatches read up to a fraction of a second.