Top left is the length, in cm. The card top right turns it into metres; the card bottom right turns those metres back into cm. Each card shows whether it divides or multiplies: "÷100" or "×100".
Why divide by 100?
1 m = 100 cm. So:
- 100 cm = 1 m
- 200 cm = 2 m
- 300 cm = 3 m
- 350 cm = 3.5 m
Going from cm to m regroups every 100 centimetres into one metre. That is why 350 ÷ 100 = 3.5.
A bigger unit means a smaller number
350 cm and 3.5 m are the same length. Each metre is bigger, so it takes fewer of them to cover it. That is the answer to "the metre is the bigger unit, so why is the number smaller?"
Check it the other way
Turn 3.5 m into cm and you get 3.5 × 100 = 350 cm. The card bottom right on the board shows "×100". Reverse the direction and ÷100 becomes ×100.
Try it yourself
Change the length on the board.
| Length | cm → m (÷100) | m → cm (×100) |
|---|---|---|
| 100 cm | 1 m | 100 cm |
| 250 cm | 2.5 m | 250 cm |
| 350 cm | 3.5 m | 350 cm |
| 1,234 cm | 12.34 m | 1,234 cm |
| 50 cm | 0.5 m | 50 cm |
Whatever the length, ÷100 gives metres and ×100 takes you back to cm. Anything shorter than a metre comes out below 1 in metres: 0.5 m is 50 cm.
Read next — Why is 1 m² equal to 10,000 cm²? For area it is not 100 but 10,000, because the ×100 applies to both the height and the width.