The lengths in a scale drawing are in proportion to the actual lengths of an object.
We often use a ratio to show the scale of a drawing
If we have a scale of 1:5 all of the lengths in the scale drawing are 5 times smaller than in real life
If a map has a scale of 1:5000 to find the actual distance between two points we would have to multiply the distance on the map by 5000
If two points are 10 cm apart on the map they are 10 cm × 5000 apart in real life
10 cm × 5000 = 50000 cm
50000 cm = 500 m
Example: A map has a scale 1:20000
The actual distance between two towns is 12km
Find the distance between the two towns on the map
Give your answer in cm
We can convert 12 km into cm first
To convert km to metres we times by 1000
To convert metres into centimetres we times by 100
12 km = 12000 m = 1200000 cm
The real life distance is 20000 times bigger than the distance on the map
To find the distance on the map we need to divide the real distance by 20000
1200000⁄20000 = 120⁄2 = 60 cm
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