Millimetres

In your book, Maths Mela (Chapter 5, Far and Near), we measure small things like a sprout, small screws and a nail. Look at a scale: between the 1 cm mark and the 2 cm mark there are small marks. They divide 1 cm into 10 equal parts, and each part is 1 millimetre (mm). So 1 cm = 10 mm. Millimetres help us measure more exactly.

A line 3 cm 6 mm long is 30 mm + 6 mm = 36 mm. To draw a line of 36 mm, draw 3 cm and then 6 small marks more. In the same way, 67 mm = 6 cm 7 mm, and the book shows 89 mm = 80 mm + 9 mm = 8 cm 9 mm. Going the other way, 4 cm 5 mm = 40 mm + 5 mm = 45 mm.

Here are all the units together: 10 mm = 1 cm, 100 cm = 1 m, and 1,000 m = 1 km. We use the same idea every time. 6 m 34 cm = 600 cm + 34 cm = 634 cm. 5,792 cm = 5,700 cm + 92 cm = 57 m 92 cm.

For kilometres, remember 1 km = 1,000 m. 6,870 m = 6,000 m + 870 m = 6 km 870 m. And 29 km 30 m = 29,000 m + 30 m = 29,030 m. Be careful with the empty places: 30 m is not 300 m.