Idea 9of 22Builds onCount the spaces from the start
10 millimetres make 1 centimetre
What are the tiny marks between the centimetres for?
Today you'll discover
- what one small space is
- how to read whole centimetres and the small spaces past them
- how to write it all in millimetres
Think firstA pencil that ends past the 8
The pencil ends 4 small marks past the 8. How long is it in millimetres?
Decide first, then press Next. Look at the small marks past the last number.
A pencil above a 12 cm ruler with millimetre marks, starting at 0. Numbered jumps count 8 whole centimetres, and a small bracket marks 4 millimetres more. The reading says 8 cm 4 mm = 84 mm. The last step shows a crayon that ends 2 small marks past the 9.
See the whole ideathe big idea and the key word, in one place
The big idea
A centimetre is 10 millimetres, so 8 cm 4 mm is 84 mm.
Ten in every centimetre
Each whole centimetre is ten millimetres.
- 1 cm10 mm
- 8 cm80 mm
- 8 cm 4 mm84 mm
Easy to get wrongDon't add centimetres and millimetres together: 8 cm 4 mm is 84 mm, not 12 mm.
Key word
- millimetre mark
- one of the small lines between the centimetres on a ruler; each space is 1 mm
Ready to use it?
- Read a length in centimetres and millimetres.
- Write it in millimetres.