Applications of Ratio and Proportion

Mathematics — First Preparatory

The drawing scale

A drawing scale is the ratio between a length on a drawing and the real length it represents.
It is usually written as 1 : n, where n is a large number.
If the scale is 1 : 20000, then every 1 cm on the drawing represents 20000 cm in reality.
The rules are:

Real length = length on the drawing × n.
Length on the drawing = real length ÷ n.
Both lengths must be in the same unit before we calculate.
Convert the real length into the unit of the drawing first, for example from metres to centimetres.

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