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Grade 4/ Maths/ Measuring Length
Chapter 6 · NCERT Class 4 Maths Mela

Measuring Length

How tall are you? How far is your school? We measure short things in centimetres, rooms in metres and journeys in kilometres. Tap each idea to explore it.

📏 3 topics⏱ ~18 min📝 10-question quiz
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Six length ideas

Length tells us how long or far. Tap each term to see what it means, with an example.

Explore · Lengthtap a term

Learn

The three big ideas

  • We measure short things in centimetres (cm), rooms and people in metres (m), and journeys in kilometres (km).
  • 1 metre = 100 centimetres and 1 kilometre = 1000 metres.
  • Pick the right unit: a pencil in cm, a cricket pitch in m, a trip to the next town in km.

Worked example. Would you measure the length of your classroom in cm, m, or km?

A classroom is a few times your height, so metres (m) is the best unit.

  • Line up one end of the object with the 0 mark, not the edge of the ruler.
  • Read the number at the other end — that is the length in cm.
  • The big numbered lines are centimetres; the tiny lines between are millimetres.

Worked example. A crayon starts at 0 and ends at the 8 mark on the ruler. How long is it?

From 0 to 8 is 8 cm long.

  • To add lengths, make sure they are in the same unit first, then add.
  • To change metres to cm, multiply by 100; to change cm to metres, share by 100.
  • 1 m 50 cm means 100 cm + 50 cm = 150 cm.

Worked example. Two ribbons are 40 cm and 60 cm. Joined together, how long are they — in cm and in m?

40 + 60 = 100 cm, and 100 cm = 1 m.

Common mix-up: Always measure from 0 on the ruler. Starting from the metal edge or the 1 mark gives a wrong, too-long answer.

Where you’ll meet it

Measuring around us

Tailoring clothes

A tailor measures your sleeve and waist in cm to stitch clothes that fit just right.

Sports day

Long jump and races are measured in metres to find the winner fairly.

Travel and maps

Road signs show distances in km so travellers know how far the next town is.

Check yourself

Quick quiz

Ten friendly questions — mostly multiple-choice with one assertion–reason — to check you can measure and compare lengths.

Score 0/10

Interactive built to the OpenMAIC approach (THU-MAIC, MIT). Content from the NCERT Class 4 Maths Mela textbook (ncert.nic.in).

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