Maths · Ratio & Proportion
Scale (maps & drawings)
Use scale factors on maps and technical drawings.
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What is a scale?
A scale shows how distances on a map or drawing compare to real life. For example, 1 cm on paper might represent 100 cm (or 1 metre) in reality. This ratio helps us shrink large objects or places to fit on paper.
Reading a scale
Scales are written as ratios like 1:50 or 1:1000. The first number shows the map distance. The second shows the real distance. A scale of 1:200 means 1 cm on the map equals 200 cm in real life.
Finding real distances
To find a real distance, multiply the map distance by the scale factor. If the map distance is 3 cm and the scale is 1:500, the real distance is 3 × 500 = 1500 cm.
Finding map distances
To find a map distance, divide the real distance by the scale factor. If a room is 800 cm long and the scale is 1:100, the map length is 800 ÷ 100 = 8 cm.
Converting units
Often you need to convert units at the end. Remember: 100 cm = 1 m and 1000 m = 1 km. A result of 150000 cm can be written as 1500 m or 1.5 km.
Worked examples
1. A map has a scale of 1:20000. Two towns are 5 cm apart on the map. What is the real distance in metres?
- The scale is 1:20000, so 1 cm on the map equals 20000 cm in real life.
- Map distance = 5 cm, so real distance = 5 × 20000 = 100000 cm.
- Convert to metres: 100000 cm ÷ 100 = 1000 m.
2. A garden is 12 m long. On a drawing with scale 1:50, how long should it be in cm?
- Real length = 12 m = 1200 cm.
- Scale is 1:50, so divide the real distance by 50.
- Drawing length = 1200 ÷ 50 = 24 cm.
3. A floor plan uses a scale of 1:100. A wall is drawn as 7.5 cm. What is the actual length in metres?
- Scale 1:100 means multiply the drawing measurement by 100.
- Actual length = 7.5 × 100 = 750 cm.
- Convert to metres: 750 ÷ 100 = 7.5 m.
Try it yourself
A map scale is 1:5000. A path measures 8 cm on the map. What is the real distance in metres?
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