RBSE Solutions Class 5 Maths Chapter 16 Geometry Important Questions

Multiple Choice Questions

Question 1. Angle less than right angle is known as
(a) Obtuse angle
(b) Right angle
(c) Acute angle
(d) Straight angle
Answer: (c) Acute angle
In simple words: An acute angle is a type of angle that is smaller than a right angle, meaning it measures less than 90 degrees. Think of it as a sharp corner.

🎯 Exam Tip: Remember the basic definitions: acute (less than 90°), right (exactly 90°), and obtuse (between 90° and 180°).

Question 2. Walls of home are made up
(a) at right angle
(b) at obtuse angle
(c) at acute angle
(d) at straight angle
Answer: (a) at right angle
In simple words: The walls in a house usually meet at a perfect square corner, which is called a right angle. This makes the house stable and easy to build.

🎯 Exam Tip: Visualize common objects around you to understand angle types; a corner of a room is a great example of a right angle.

Question 3. Obtuse angle called
(a) to 90° angle
(b) to 180° angle
(c) to 60° angle
(d) to 135° angle
Answer: (d) to 135° angle
In simple words: An obtuse angle is any angle that is bigger than 90 degrees but smaller than 180 degrees. From the options, 135 degrees is a perfect example of an obtuse angle.

🎯 Exam Tip: When given options, look for the one that correctly fits the definition of the angle type asked. Always check if the angle is greater than 90° and less than 180°.

Question 4. Angle shown in the following figure known as
(a) Acute angle
(b) Right angle
(c) Obtuse angle
(d) Straight angle
Answer: Figure missing from source.
In simple words: (Cannot be determined without the figure.)

🎯 Exam Tip: If a question refers to a figure, always ensure the figure is visible and clear before attempting to answer.

Question 5. Those angles which are greater than right angle known as
(a) Straight angle
(b) Right angle
(c) Obtuse angle
(d) Acute angle
Answer: (c) Obtuse angle
In simple words: An angle that is larger than 90 degrees (a right angle) but smaller than 180 degrees (a straight angle) is known as an obtuse angle. It looks wide open.

🎯 Exam Tip: Understand the relative sizes of angles compared to a right angle (90°) and a straight angle (180°).

Question 6. 40° angle is called ............
(a) Obtuse angle
(b) Straight angle
(c) Right angle
(d) Acute angle
Answer: (d) Acute angle
In simple words: Since 40 degrees is less than 90 degrees, it falls into the category of an acute angle. Acute angles are small and sharp.

🎯 Exam Tip: Always compare the given angle measure to 90° and 180° to correctly classify it.

Question 7. 90° angle is called in the following
(a) Right angle
(b) Acute angle
(c) Obtuse angle
(d) Straight angle
Answer: (a) Right angle
In simple words: An angle that measures exactly 90 degrees is always called a right angle. It forms a perfect 'L' shape.

🎯 Exam Tip: A right angle is a fundamental reference point for other angle classifications.

Question 8. 120° angle is known as
(a) Acute angle
(b) Right angle
(c) Obtuse angle
(d) Straight angle
Answer: (c) Obtuse angle
In simple words: Because 120 degrees is larger than 90 degrees but smaller than 180 degrees, it is an obtuse angle. It's wider than a right angle.

🎯 Exam Tip: Practice classifying various angle measures to quickly identify them in tests.

Fill In The Following Blanks

Question 1. Fill in the following blanks
1. Every right angle is of measure ............ .
2. Tool used to measure angle is known as ............ .
3. 180° angle is called ............ .
4. All walls of our home is made up at ............ .
5. Angle greater than 90° and less than 180° is called ............ .
6. Those angle which are smaller than right angle are called ............ .
7. Angle whose measure is 90° is called ............ .
Answer:
1. Every right angle is of measure 90°.
2. Tool used to measure angle is known as Protractor.
3. 180° angle is called Straight angle.
4. All walls of our home is made up at Right angle or 90°. They form a strong structure.
5. Angle greater than 90° and less than 180° is called Obtuse angle.
6. Those angle which are smaller than right angle are called Acute angle.
7. Angle whose measure is 90° is called Right angle.
In simple words: We are filling in the missing words for different types of angles and the tool used to measure them. Each blank needs a specific term like 90°, protractor, or a name for an angle type.

🎯 Exam Tip: Memorize the definitions and key properties of different angles and the names of geometry tools to fill in blanks accurately.

Very Short Answer Type Questions

Question 1. Write the type of the angle formed between the two hands of watch given below.
Answer: (Assuming the clock hands are showing a time like 4:00 or 5:00, forming a wide angle.) It forms an Obtuse angle because the angle is greater than a right angle (90 degrees). An obtuse angle is visually wider than a right angle.
In simple words: If the clock hands form a wide angle, bigger than a corner, it's an obtuse angle.

🎯 Exam Tip: When a figure is implied, try to imagine a typical representation that would lead to the given answer. Often, clock hands are used to demonstrate angles.

Question 2. Write the type of the angle formed between the two hands of following watch.

Answer: The clock hands are at 12 and 6, forming a straight line. This is a Straight angle. A straight angle measures exactly 180 degrees.
In simple words: When the clock hands point in opposite directions, like at 6 o'clock, they make a straight line, which is called a straight angle.

🎯 Exam Tip: A straight angle is formed by two rays going in opposite directions from a common endpoint, creating a 180-degree turn.

Question 3. Write the type of angle formed between hands of following watch.

Answer: The clock hands are at 12 and 3, forming a perfect 'L' shape. This is a Right angle. A right angle measures exactly 90 degrees.
In simple words: When the clock hands are at 12 and 3, or 9 and 12, they form a right angle, which looks like a perfect corner.

🎯 Exam Tip: Recognizing right angles in everyday objects, like clock faces or table corners, helps in quickly identifying them.

Question 4. Write down the types of following angles.
Answer:
(i) (Figure missing, implied to be 90°) Right angle. A right angle measures exactly 90 degrees.
(ii) (Figure missing, implied to be less than 90°) Acute angle. An acute angle measures less than 90 degrees.
(iii) Obtuse angle. This angle is wider than 90 degrees. It measures between 90 and 180 degrees.
(iv) Acute angle. This angle is smaller than 90 degrees. It appears sharp.
In simple words: We look at each angle to see if it's smaller than a right angle (acute), exactly a right angle, or bigger than a right angle (obtuse).

🎯 Exam Tip: Pay attention to the size and shape of the angle opening to correctly classify it. Practice drawing examples of each type.

Question 5. Write the definition of straight angle.
Answer: A straight angle is an angle that measures exactly 180 degrees. It forms a straight line. It is also equal to two right angles placed side-by-side.
In simple words: A straight angle is like a flat line and measures 180 degrees.

🎯 Exam Tip: Remember that a straight angle is equivalent to half a full circle or two right angles.

Question 6. Which angle is greater than right angle and less than two right angles ?
Answer: The angle that is greater than a right angle (90 degrees) and less than two right angles (180 degrees) is an Obtuse angle. This describes its exact range.
In simple words: An obtuse angle is wider than a 90-degree corner but not as wide as a straight line.

🎯 Exam Tip: Defining an angle by its range (e.g., between 90° and 180°) is crucial for precise classification.

Question 7. How angle is formed.
Answer: An angle is formed when two rays (or lines or line segments) meet at a common point, called the vertex. It represents the amount of rotation between these two rays. Angles show a change in direction or spin.
In simple words: An angle is made when two lines meet at one point, showing how much they spread apart.

🎯 Exam Tip: The key components of an angle are its two arms (rays) and a vertex (the common point where they meet).

Question 8. How many types angles are ?
Answer: There are four main types of angles that are commonly taught:
(i) Right angle (measures exactly 90 degrees)
(ii) Acute angle (measures less than 90 degrees)
(iii) Obtuse angle (measures greater than 90 degrees but less than 180 degrees)
(iv) Straight angle (measures exactly 180 degrees)
In simple words: There are four main kinds of angles: acute (small), right (corner), obtuse (wide), and straight (flat line).

🎯 Exam Tip: List the four basic angle types with their degree ranges to get full marks on this question.

Short Answer And Essay Type Questions

Question 1. Measure the angles given below with the help of a protractor.
(1)
(2)
(3)
Answer: By carefully using a protractor:
(1) The angle measures 90°. This is a right angle.
(2) The angle measures 60°. This is an acute angle.
(3) The angle measures 115°. This is an obtuse angle.
In simple words: Using a protractor, we find that the first angle is 90 degrees, the second is 60 degrees, and the third is 115 degrees.

🎯 Exam Tip: Always place the protractor's center exactly on the vertex and align one arm with the 0° line to get an accurate reading.

Question 2. Measure the following angles with the help of protractor :
(i)
(ii)
(iii)
Answer: Using a protractor to measure each angle:
(i) The angle measures 70°. It is an acute angle.
(ii) The angle measures 115°. It is an obtuse angle.
(iii) The angle measures 90°. It is a right angle.
In simple words: We measured the given angles using a protractor and found them to be 70 degrees, 115 degrees, and 90 degrees.

🎯 Exam Tip: Double-check your protractor alignment and reading to avoid common errors in angle measurement.

Question. Identify Angles Less Than A Right Angle In The Following Figures.
Answer: We need to identify angles that are less than 90 degrees (acute angles) in each figure. 'O' marks acute angles, while 'X' marks angles that are right or obtuse.
(i)
(ii)
(iii)
(iv)
(v)
(vi)
In simple words: We marked angles smaller than 90 degrees with an 'O' and other angles with an 'X' in each shape.

🎯 Exam Tip: To identify acute angles, look for vertices that appear sharper than a square corner. Use the corner of a paper as a quick reference.

If we look carefully at the floor, walls and ceiling of any building then we see a particular inclination in the corners of floor, walls and ceiling.

Ceiling

Floor
(Room figure) (3 o'clock) (9 o' clock)

See carefully the hour and minute hands of a clock at 3 o'clock and 9 o'clock. We found that they are in the same position with each other as we have seen the inclination walls and floor. This particular inclination is known as right angle. Therefore, such an angle between two planes or lines is known as right angle. It is expressed by

Essay Type Questions

Question 1. Give the estimated method of angle measurment (right angle, acute angle and obtuse angle) on the basis of a paper.
Answer: To estimate angles using paper, follow these steps:
1. Take one transparent paper and cut out a circular piece. A circular shape is useful for visualizing rotations.
2. Fold the circle exactly in half from the middle. This creates a straight line.
3. Now, fold the paper again, exactly in half, across the fold you just made. This will create a perfect corner.
4. Open the paper and cut along with any one of the folded lines. The corner formed by the two folds is a right angle (90 degrees).
5. Use this right angle to compare other angles:
* If an angle is smaller than your paper right angle, it's an **Acute angle**.
* If an angle is exactly the same size as your paper right angle, it's a **Right angle**.
* If an angle is larger than your paper right angle, but smaller than the full straight fold (180 degrees), it's an **Obtuse angle**.

In simple words: You can make a 90-degree corner by folding a paper circle twice. Then use this paper corner to check if other angles are smaller (acute), the same (right), or bigger (obtuse).

🎯 Exam Tip: Explaining the paper-folding method step-by-step shows a practical understanding of angle construction and comparison.