Scale
What is scale?
- In mathematics, scale can have many meanings, but in accurate drawings and constructions scale refers to a ratio
- Maps and technical drawings are usually drawn to a scale
- The scale chosen will depend on the area being mapped out
- A map of a classroom will use a large scale and can show a lot more detail
- A map of a country or a world map will use a small scale and can show a much bigger area but in less detail
- Scale can be given as a description, for example "1 cm on the diagram represents 2 m in real life"
- Scale can be given as a ratio, for example "the scale on the map is 1 : 10 000"
How do I convert between a scale length and a real length?
- If you are converting from a scale length to a real length, normally you have to multiply
- For example, if the scale is "1 cm on the diagram represents 2 m in real life"
- to convert 6 cm on the diagram to the real-life measurement, we need to multiply by 2 and change the units to m
- So 6 cm = (6 × 2) m = 12 m
- For example, if the scale is "1 cm on the diagram represents 2 m in real life"
- If you are converting from a real length to a scale length, normally you have to divide
- For example, if the scale is "1 cm on the diagram represents 2m in real life"
- to convert 15 m in real life to the length on the diagram, we need to divide by 2 and change the units to cm
- So 15 m = (15 ÷ 2) cm = 7.5 cm
- For example, if the scale is "1 cm on the diagram represents 2m in real life"
Examiner Tip
- If the scale is not given in unit form (1 : n), then it may help to convert it to unit form first
Worked example
On a scale drawing of a bridge, 1 cm represents 12 m.
The distance from one side of the bridge to the other is 300 m.
Find this distance on the scale drawing.
Divide the real-life distance by 12
300 cm ÷ 12 = 25
Change the units from m to cm
25 cm