GCSE Maths revision · Ratio and proportion

Scale drawings and maps

Foundation and Higher

The idea

A map scale such as 1:25 0001 : 25\,000 means 1 cm1\text{ cm} on the map is 25 000 cm25\,000\text{ cm} in real life, which is 250 m250\text{ m}.

  1. Map to real: multiply by the scale.
  2. Real to map: divide by the scale.
  3. Convert units at the end: 100 cm=1 m100\text{ cm} = 1\text{ m}, 1000 m=1 km1000\text{ m} = 1\text{ km}.

Watch out Keep the units the same on both sides of the scale before you convert.

See it worked

Worked exampleNon-calculator4 marks

A map has a scale of 1:50 0001 : 50\,000.

(a) Two villages are 44 cm apart on the map. Work out the real distance between them in kilometres.

(b) Two farms are 3.53.5 km apart. How far apart are they on the map, in centimetres?

  1. (a) 4×50 000=200 0004 \times 50\,000 = 200\,000 cm.
  2. 200 000 cm200\,000\,\mathrm{cm} =2000 m= 2000\,\mathrm{m} =2 km= 2\,\mathrm{km}.
  3. (b) 3.53.5 km =350 000= 350\,000 cm.
  4. 350 000÷50 000=7 cm350\,000 \div 50\,000 = 7\,\mathrm{cm}.

Answer (a) 22 km; (b) 77 cm

Your turn

Question 1Non-calculator3 marks

A plan uses a scale of 1 : 80. A wall is 6.5 cm long on the plan. Work out its actual length in metres.

Question 2Non-calculator4 marks

A scale drawing shows a 5 m wall as 10 cm. A second wall is 7.5 cm on the drawing.

(a) Find the scale in the form 1:n.

(b) Find the actual length of the second wall in metres.

Question 3Non-calculator5 marks

Map A has a scale of 1:25 0001 : 25\,000. Map B has a scale of 1:40 0001 : 40\,000.

(a) A lake is 88 cm long on map A. How long is the lake on map B?

(b) On map A, the area of the lake is 12 cm212\ \text{cm}^2. Work out the real area of the lake in km2\text{km}^2.

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