Idea 20of 22Builds onMove the digits to change the unit
Small unit to big unit: divide
How do you write 250 cm in metres?
Today you'll discover
- why the number must shrink
- what to divide by
- where the decimal comes from
Think firstA ribbon 250 cm long
A ribbon is 250 cm long. How many metres is that?
Decide first, then press Next. Watch the small units gather into big ones.
A ribbon drawn as a bar, 250 cm. Under it, a ruler strip marked 0, 50, 100 … 250 cm; then the same length grouped into tiles of 1 m, 1 m and 0.5 m. The working reads 250 cm = 2.5 m, 250 ÷ 100 = 2.5. The last step shows 1500 mL of water.
See the whole ideathe big idea and the key word, in one place
The big idea
Small unit to big unit: divide, because fewer big units fit: 250 cm = 2.5 m.
There and back
Multiply one way, divide the other: the same 100 either way.
- m to cm× 100
- cm to m÷ 100
Easy to get wrongDividing by 100 moves the digits 2 places right: 250 becomes 2.5.
Key word
- converting up
- writing an amount in a bigger unit; you divide
Ready to use it?
- Write a small-unit amount in a bigger unit, with a decimal.