Measuring Length — NCERT Solutions

Given: The picture shows students measuring the depth of something (e.g., a well or container).

From the picture, the students are measuring depth.

Tick marks (✓):

• a) Length ✓ (depth is a form of length measurement)
• b) Height ✓ (height is also a form of length measurement)
• c) Weight ☐ (not being measured)
• d) Depth ✓ (already ticked — this is what is directly shown)
• e) Breadth ✓ (breadth is also a form of length measurement)
• f) Temperature ☐ (not being measured)

Note: As the teacher's note explains, height, width, depth, and breadth all refer to length measurement. So length, height, breadth, and depth can all be ticked.

Given: The picture shows students measuring height.

Answer:
A measuring tape (or metre scale/metre rope) is being used to measure the height in the picture.

Other tools that can be used to measure height:

1. A metre scale (ruler)
2. A metre rod
3. A measuring tape used by tailors
4. A metre rope

All these tools help us find out how tall (high) something is.

Given: We need to check each statement against real classroom observations. (Answers may vary; typical expected answers are given below.)

Concept: 1 metre = 100 cm. Average height of Class 4 students ≈ 120–140 cm (more than 1 m). Arm length ≈ 50–60 cm (less than 1 m). Door height ≈ 200 cm (more than 1 m). Blackboard breadth ≈ 150–200 cm (more than 1 m).

a) The height of most of the students in my grade is more than a metre. → Correct (Most Class 4 students are taller than 1 m.)

b) The length of my arm is less than a metre. → Correct (An arm is usually about 50–60 cm, which is less than 100 cm = 1 m.)

c) The height of the door of the grade is less than a metre. → Incorrect (A standard door is about 2 m tall, which is more than 1 m.)

d) The breadth of the blackboard is more than a metre. → Correct (A classroom blackboard is usually more than 1 m wide.)

Given: We have a 1 m rope.

How to make the lines:

• 1 m line: Place the 1 m rope on the floor and draw a line along it. This gives a 1 m line.
• 5 m line: Place the 1 m rope end-to-end 5 times on the floor, marking each end. Join the marks to get a 5 m line.
• 10 m line: Place the 1 m rope end-to-end 10 times on the floor, marking each end. Join the marks to get a 10 m line.

Activity: Walk, jump, and crawl along each line to get a feel for how long 1 m, 5 m, and 10 m are.

This is a hands-on activity. Results will vary for each student.

Given: Students perform a long jump and measure the distance using 1 m, ½ m, and ¼ m ropes.

How to measure:

• After each jump, place the 1 m rope from the starting line to where the student landed.
• If the distance is more than 1 m, use the 1 m rope first, then use the ½ m or ¼ m rope for the remaining part.
• Record whether the jump is less than 1 m, equal to 1 m, or more than 1 m.

Sample filled table (answers will vary for each class):

Students should fill in their own classmates' names and measurements.

Given: We need to estimate and then measure the length and breadth of the classroom.

How to measure:

• Use the 1 m rope repeatedly along the length of the classroom, counting how many times it fits.
• Do the same for the breadth.

Sample answer (will vary by classroom):

• Estimated length of classroom: about 8 m
• Actual length of classroom: 8 m (measured using the 1 m rope 8 times)
• Estimated breadth of classroom: about 6 m
• Actual breadth of classroom: 6 m (measured using the 1 m rope 6 times)

Students should record their own classroom's measurements.

Given: Pictures of a bus and a cricket bat are shown (images not visible, but standard sizes are used).

Standard lengths:

• Length of one bus ≈ 12 metres (a standard city bus is about 12 m long)
• Length of one cricket bat ≈ 1 metre (a standard cricket bat is about 96 cm ≈ 1 m)

Answer:

• Length of one bus = approximately 12 m
• Length of one cricket bat = approximately 1 m

(Answers may vary slightly depending on the values given in the pictures in the textbook.)

Given: (Based on typical textbook values)

• Length of one blue whale ≈ 30 m
• Length of two blue whales = 30 × 2 = 60 m
• Length of one bus ≈ 12 m

Calculation:
$$\text{Number of buses} = \frac{60}{12} = 5$$

Answer: 5 buses would be equal to the length of two blue whales.

(Note: If the textbook uses different values for bus/whale length, apply the same method with those values.)

Given: (Based on typical textbook values)

• Length of one blue whale ≈ 30 m
• Length of one cricket bat ≈ 1 m

Calculation:
$$\text{Number of cricket bats} = \frac{30 \text{ m}}{1 \text{ m}} = 30$$

Answer: 30 cricket bats will be needed to measure one whale.

(Apply the same method if the textbook gives different values.)

Given: (Based on typical textbook values)

• Height of one ostrich ≈ 2.5 m
• Height of two ostriches stacked = 2.5 × 2 = 5 m

Looking at the picture clues, two ostriches stacked would be equal to the height of a giraffe (a giraffe is about 5 m tall).

Answer: If two ostriches stand one above another, their height will be equal to the height of a giraffe.

(Answer depends on the picture values given in the textbook.)

Given: (Based on typical textbook values)

• Length of one blue whale ≈ 30 m
• Length of one crocodile ≈ 5 m

Calculation:
$$\text{Number of crocodiles} = \frac{30}{5} = 6$$

Answer: 6 crocodiles will be equal to the length of a blue whale.

(Apply the same method if the textbook gives different values for crocodile length.)

Given: 1 metre (m) = 100 centimetre (cm)

Finding $\frac{1}{2}$ m in cm:
$$\frac{1}{2} \text{ m} = \frac{1}{2} \times 100 \text{ cm} = 50 \text{ cm}$$

Finding $\frac{1}{4}$ m in cm:
$$\frac{1}{4} \text{ m} = \frac{1}{4} \times 100 \text{ cm} = 25 \text{ cm}$$

Answer:
$$\frac{1}{2} \text{ m} = \boxed{50} \text{ cm}, \quad \frac{1}{4} \text{ m} = \boxed{25} \text{ cm}$$

Given: Various objects are shown in the pictures (images not visible, but the method is described).

How to measure:

• Place the object along the scale starting from the 0 cm mark.
• Read the measurement at the other end of the object.
• Record the length in cm.

To write in increasing order:

• Measure each object and note its length.
• Arrange from the shortest (smallest cm) to the longest (largest cm).

Example (actual measurements will depend on the pictures):
If the objects are a pencil (10 cm), an eraser (4 cm), a sharpener (2 cm), and a crayon (7 cm), then increasing order would be:
$$\text{Sharpener (2 cm) < Eraser (4 cm) < Crayon (7 cm) < Pencil (10 cm)}$$

Students should measure the actual objects shown in their textbook and write the order accordingly.

Given: We need to estimate and then measure each item.

Concept: 1 cm is the length of one small division on a ruler. It is roughly the width of a fingernail.

Expected answers (typical values; actual measurements may vary):

Examples of things less than or equal to 1 cm:

• A grain of rice
• A sesame seed (til)
• An ant
• A mustard seed

Students should verify by actually measuring with a scale.

Given: Three toy cars are rolled down a ramp and the distance each travels is measured.

How to measure:

• Place the measuring tape from the bottom of the ramp to where the car stops.
• Read the measurement in cm.
• Rank: Car that travels the farthest = Rank 1; shortest distance = Rank 3.

Sample answer (actual values will vary):

Students should fill in their own measured values.

Given: A treasure hunt map is shown on a dot grid where 1 square = 1 cm (images not fully visible).

Method:

• Trace each possible route on the yellow tiles.
• Count the number of 1 cm squares (tiles) along each route.
• The route with the most tiles is the longest route.
• The route with the fewest tiles is the shortest route.

Answer: (Will depend on the actual map in the textbook)

• Count each tile step as 1 cm.
• Add up all the steps for each route.
• Compare and identify the longest and shortest routes.

Students should trace the routes in their textbook map and count the tiles to find the lengths in cm.

Given: Students trace their own hand and measure its length.

How to measure:

• Trace your hand on paper with fingers together.
• Place the scale from the bottom of the palm (wrist line) to the tip of the longest finger (middle finger).
• Read the measurement.

Sample answer:
Length of my hand = 15 cm (This will vary for each student; typical range for Class 4 students is 13–17 cm.)

Students should measure their own hand and write the actual value.