Level 1 · Ages 6–8
Read it again any time, including while you work through the exercises.
You already know how to measure in centimetres. But imagine measuring the distance between two towns in centimetres... you would need millions of ruler marks! For every size of object, there is a handy unit.
The centimetre (cm) is for small objects: a pencil, a hand, a book. Even smaller, the millimetre (mm) measures tiny things, like the thickness of a coin.
The metre (m) is for big objects: a door, a table, a playground. Remember this magic equality: 1 metre = 100 centimetres. One metre is one hundred little centimetres lined up!
The kilometre (km) is for long distances: the way from home to the swimming pool, the road between two towns. And here too, an equality to remember: 1 kilometre = 1000 metres.
Choosing the right unit is like choosing the right pair of shoes: not too big, not too small. You do not measure an ant in kilometres, nor a motorway in millimetres!
A rope is 3 metres long. How much is that in centimetres?
1 m = 100 cm
I remember the key equality: in 1 metre there are 100 centimetres.
3 m = 3 × 100 cm
The rope is 3 metres, so 3 groups of 100 centimetres.
3 × 100 = 300
I compute: 3 times 100 makes 300.
Result: 3 m = 300 cm