Metres and centimetres

In your book, Maths Mela (Chapter 5, Far and Near), Shikha and Sonu are measuring saris and stoles at the village weaving centre. Some lengths are written in centimetres and some in metres, and they want to find which ones are the same. The key fact is 1 m = 100 cm. So 2 m = 200 cm, 4 m = 400 cm, 5 m = 500 cm and 7 m = 700 cm.

A length can be written in more than one way. 204 cm = 200 cm + 4 cm = 2 m 4 cm. But 240 cm = 200 cm + 40 cm = 2 m 40 cm, a different length. And 540 cm = 5 m 40 cm.

Sometimes the centimetres are more than 100. 6 m 150 cm = 600 cm + 150 cm = 750 cm. Since 150 cm is 1 m 50 cm, this is also 7 m 50 cm. In the same way, 2 m 204 cm = 200 cm + 204 cm = 404 cm, which is 4 m 4 cm.

Ritika compares the lengths of rods. To compare, change both lengths to centimetres first. 456 cm and 5 m: 5 m = 500 cm, so 456 cm < 5 m. 6 m 5 cm = 605 cm and 6 m 50 cm = 650 cm, so 6 m 5 cm < 6 m 50 cm. 2 m 150 cm = 350 cm and 3 m 50 cm = 350 cm, so they are equal. And 138 cm + 1 m = 138 cm + 100 cm = 238 cm, so 238 cm = 138 cm + 1 m.