NCERT Class 4 Mathematics Maths Mela Chapter 06 Measuring Length PDF Download

Chapter 6: Measuring Length

Let Us Observe

Note for Teachers: The words tall, wide, short and long are used in daily life. Discuss with students that height, width, depth, breadth all refer to length measurement. These words are used depending on different situations and orientation. At this point students only need to understand that all these words denote length.

[Figure: Students measuring height during a school health programme, See in your textbook]

1. Look at the picture. What are the students measuring? Put a tick mark (✓) if you find it being measured.
   • a) Length
   • b) Height
   • c) Weight
   • d) Depth
   • e) Breadth
   • f) Temperature
2. What is being used to measure the height? What other tools can be used to measure height?
3. Recall in Grade 3 you studied that lengths are measured in metres. Check and fill in the blanks whether the following are correct/incorrect for your classroom.
   • a) The height of most of the students in my grade is more than a metre. _______________
   • b) The length of my arm is less than a metre. _______________
   • c) The height of the door of the grade is less than a metre. __________
   • d) The breadth of the blackboard is more than a metre.___________

Measuring is Fun

Remember we made, 1 metre (m), half metre (\( \frac{1}{2} \) m), and quarter metre (\( \frac{1}{4} \) m) ropes. Let us make them again.

[Figure: Ropes showing 1 m, two half metre ropes, and four quarter metre ropes, See in your textbook]

Do you notice \( 1 \text{ m} = \frac{1}{2} \text{ m} + \frac{1}{2} \text{ m} \) and \( 1 \text{ m} = \frac{1}{4} \text{ m} + \frac{1}{4} \text{ m} + \frac{1}{4} \text{ m} + \frac{1}{4} \text{ m} \) and \( \frac{1}{2} \text{ m} = \frac{1}{4} \text{ m} + \frac{1}{4} \text{ m} \).

Let Us Do

Use your ropes to carry out the following activities. You can use a combination of ropes, if needed.

1. Walk, Jump, and Crawl on 1, 5 and 10 m line

   Draw lines of 1 m, 5 m, and 10 m on the floor of the classroom or outside in the playground.

   How will you make these lines? Think and share with your friends. Walk, jump, and crawl on the lines.

   Note for Teachers: Making the lines by repeatedly using metre rope and walking, jumping and crawling on the lines will help students develop an estimate of how big 5 m and 10 m is. They will be able to use this experience to estimate and compare other lengths in their surroundings.

2. Long Jump

   Each child can participate in a long jump competition. How far have your friends jumped? Measure as accurately as possible using a combination of ropes. Who jumped the longest distance?

   Fill the following table.

   Name of the student	Estimated length of the jump			Actual measurement
   	Less than 1 m	1 m	More than 1 m

   Who has jumped the shortest?

   Note for Teachers: Allow children to measure 100 m using their footsteps and note how many footsteps fit in 100 m. This can be used for further estimations.

3. Estimate how long and broad is your classroom. Measure and check.

   [Figure: Two students measuring the breadth of their classroom with a metre rope, See in your textbook]

Teacher's Note

When you measure with ropes, always align the rope in a straight line and make sure the starting point is at zero. Using combined ropes helps you understand that lengths can be made up of smaller units - just like the half and quarter metre pieces form a full metre.

Let Us Think: Guess the Length

[Figure: A blue whale labeled "Length about 30 metres", two buses, a giraffe in a barrel labeled "4 m", an ostrich labeled "3 m", and a crocodile labeled "Length about 6 metres", See in your textbook]

Look at the pictures carefully and answer the questions.

1. What is the length of one bus in metres? What is the length of one cricket bat in metres?
2. How many buses would be equal to the length of two blue whales?
3. How many cricket bats will be needed to measure one whale?
4. If two ostriches stand one above another, their height will be equal to the height of ______________.
5. How many crocodiles will be equal to the length of a blue whale?

Measuring Small Things

Can you think how to measure a small thing like an eraser or a rice grain?

We need a smaller unit to measure such small items. Observe a standard metre scale. You can see the scale is divided into 100 equal parts. The length of each one of these parts has a special name called Centimetre (cm).

Let Us Observe

Chutki wants to keep track of the increase in height of her plant.

Compare the metre rope with the measuring tape used by a tailor. Is the length of both the same or different?

Observe the measuring tape carefully. What do you notice?

[Figure: A measuring tape showing numbers 0 to 10 with red bars marking each centimetre, See in your textbook]

This is one centimetre.

[Figure: Two segments labeled "1 cm" and "1 cm", See in your textbook]

The length of each red bar is 1 cm.

[Figure: A measuring tape with 10 red bars showing "The length of each red bar is 1 cm.", See in your textbook]

The red bar is repeated 10 times to make 10 cm. When we repeat the length of the red bar 100 times, we will get 1 metre scale/tape.

\[ 1 \text{ metre (m)} = 100 \text{ centimetre (cm)} \]

\[ \frac{1}{2} \text{ m} = \text{ _____ cm, } \frac{1}{4} \text{ m} = \text{ _____ cm} \]

Discuss how these marks help us measure clearly.

Now use the measuring tape/scale to see how tall your plants grow every week.

Teacher's Note

A metre has 100 centimetres, so \( \frac{1}{2} \) m = 50 cm and \( \frac{1}{4} \) m = 25 cm. When you use a scale to measure, place the zero mark at the starting point and read the number where the object ends. This is the measurement in centimetres.

Key Points

• Different words like height, width, length, breadth and depth are all ways of measuring how long something is, depending on which direction you are measuring.
• A metre rope can be divided into smaller pieces: two half-metre pieces or four quarter-metre pieces, and these combine to make one full metre.
• For very small objects like erasers and rice grains, we use a smaller unit called a centimetre; one metre equals 100 centimetres.
• When measuring with ropes or scales, always keep them straight and start from the zero mark to get an accurate measurement.
• You can estimate lengths by comparing them to objects whose measurements you already know, like buses or crocodiles.

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