Skill: Measure length in centimetres

To measure an object in centimetres:

1. Put the 0 mark on the ruler exactly at one endpoint of the object.
2. Keep the ruler straight along the object.
3. Look at the mark where the other endpoint reaches.
4. Read that number. It tells the length in centimetres.

Do not count the printed numbers. The spaces between the marks are the equal $1$-centimetre units.

Example: A crayon is placed along a ruler.

• The left end of the crayon lines up with $0$.
• The right end lines up with $6$.
• So the crayon is $\boxed{6\text{ cm}}$ long.

We can check by counting the spaces from $0$ to $6$: there are six $1$-centimetre spaces.