Reading scale
Rulers and tape measures use the same metric scale.
The smallest markings or divisions on the scale are 1 mm apart.
Numbers are only written every 10 and 100 millimetres.
The following examples show how to read a metric scale on a ruler or tape measure.
Example 1
To work out the measurement at the black arrow:
- start from 0, the left hand end of the ruler (first red arrow)
- from zero look across and read the last number before the black arrow – this number is 20 (second red arrow)
- count the number of divisions between 20 and the black arrow – there are 3
- add the two numbers together
- 20 + 3 = 23 mm.
The distance from the left hand end of the ruler to the black arrow is 23 mm.
Example 2
To work out the measurement at the black arrow:
- start from 0, the left hand end of the ruler (first red arrow)
- between the left end of the ruler and the black arrow there is one 100 mark – 1 x 100 = 100 mm
- read the last number between the 100 mark and the black arrow – this equals 10 mm
- count the divisions from 10 to the black arrow – this is 5 mm
- add the three numbers together
- 100 + 10 + 5 = 115 mm.
The distance from the left hand end of the ruler to the black arrow is 115 mm.
