This super long ruler measures the heights of people.
If your height reached the mark indicated on the red arrow, how tall would you be in millimetres?
Because this ruler measures people’s heights, the numbers are the number of centimetres.
There are 4 spaces between every 10 centimetres on the ruler, so each space is worth:
10 ÷ 2 cm = 2.5 cm
2.5 cm = 25 mm because one centimetre is 10 millimetres.
The person who is the height of the red arrow is 100 cm + one space.
100 cm = 1000 mm
The person is therefore 1000 + 25 = 1025 mm tall.