Here is a question. This piece of string is one metre long, so how many centimetres long is it as well?

The converter changes lengths from one unit to another. Watch what happens to the number each time the unit changes, and see if you can spot the rule.

Today we work through these renamings together on the board, one at a time. Before each one is checked, follow along and decide for yourself: are we going to a smaller unit or a bigger unit?

1. Change 4 cm to millimetres.
2. Change 5 m to centimetres.
3. Change 60 mm back to centimetres.

Today we work through these renamings one at a time, getting trickier as we go. We will take them in turn: first 8 cm to millimetres, then 90 mm back to centimetres, then 6 m to centimetres. The last one, 325 cm to metres.

What we learned today

• The same length can be renamed: 1 m = 100 cm and 1 cm = 10 mm.
• Going to a smaller unit, we multiply (×10 or ×100), and the number gets bigger.
• Going to a bigger unit, we divide (÷10 or ÷100), and the number gets smaller.
• A leftover can be written as a mixed length, like 325 cm = 3 m 25 cm.