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R2

Use scale factors, scale diagrams and maps

Scale diagrams and maps

Worked answers, methods and verified real exam appearances for R2 on Edexcel GCSE Maths 1MA1.

Explanation

  • A scale written 1:n1:n compares a diagram length with the corresponding real length in the same units. Multiply a diagram length by nn to obtain the real length, or divide the real length by nn to obtain the diagram length.
  • Convert units only after establishing which direction the scale factor acts.
  • For areas, square the linear scale factor; for volumes, cube it.
  • On a map, measure between the stated points accurately and use any given scale bar or numerical scale.
  • Examiners award method for applying the scale in the correct direction and then converting units correctly.
A scale of 1:n1:n multiplies every diagram length by nn to give the corresponding real length.

Worked example

A map has scale 1:250001:25\,000. A route measures 6.4cm6.4\,\text{cm} on the map. Find the real distance in kilometres.

  1. 1.Real distance =6.4×25000=160000cm=6.4\times25\,000=160\,000\,\text{cm}.
  2. 2.160000cm=1600m160\,000\,\text{cm}=1600\,\text{m}.
  3. 3.1600m=1.6km1600\,\text{m}=1.6\,\text{km}.

Answer: 1.6km1.6\,\text{km}.

Common mistakes

  • Don't divide by the scale factor when converting a diagram length to a real length.
  • Don't mix centimetres and metres inside the ratio before making the units consistent.
  • Don't use nn rather than n2n^2 when a scale-diagram question asks for area.

Exam tip

Write what 1cm1\,\text{cm} represents before scaling, because this makes the direction of the conversion clear.

Worked practice

Q1
Tier 1 · Easy

1

A ranger's sketch uses scale 1:250001:25\,000. A footpath trace measures 6.4cm6.4\,\text{cm}. Find the real distance in kilometres.

(2)

(Total for Question 1 is 2 marks)

Mark scheme

Mark scheme for question 1
QuestionAnswerMarkMark scheme
1
  • 1.6km1.6\,\text{km}
26.4×25000=160000cm=1600m=1.6km6.4\times25\,000=160\,000\,\text{cm}=1600\,\text{m}=1.6\,\text{km}.
Q2
Tier 2 · Standard

2

A model theatre uses scale 1:401:40. A real doorway is 2.04m2.04\,\text{m} high. Work out the model doorway height in centimetres.

(2)

(Total for Question 2 is 2 marks)

Mark scheme

Mark scheme for question 2
QuestionAnswerMarkMark scheme
2
  • 5.1cm5.1\,\text{cm}
2The real height is 204cm204\,\text{cm}. Divide by 4040: 204/40=5.1cm204/40=5.1\,\text{cm}.
Q3
Tier 3 · Hard

3

A site plan has scale 1:25001:2500. A garden occupies 96cm296\,\text{cm}^2 on the plan. Calculate its real area in hectares. Use 11 hectare =10000m2=10\,000\,\text{m}^2.

(4)

(Total for Question 3 is 4 marks)

Mark scheme

Mark scheme for question 3
QuestionAnswerMarkMark scheme
3
  • 66 hectares
4At this scale, 1cm1\,\text{cm} represents 25m25\,\text{m}, so 1cm21\,\text{cm}^2 represents 252=625m225^2=625\,\text{m}^2. The real area is 96×625=60000m2=696\times625=60\,000\,\text{m}^2=6 hectares.
Q4
Tier 1 · Easy

4

A shape is enlarged so that a side of length 8cm8\,\text{cm} becomes 14cm14\,\text{cm}. Work out the scale factor.

(1)

(Total for Question 4 is 1 mark)

Mark scheme

Mark scheme for question 4
QuestionAnswerMarkMark scheme
4
  • 1.751.75
1The scale factor is 14÷8=1.7514\div8=1.75.
Q5
Tier 2 · Standard

5

A real wall is 18m18\,\text{m} long and is drawn as 7.2cm7.2\,\text{cm}. Write the scale of the drawing in the form 1:n1:n.

(2)

(Total for Question 5 is 2 marks)

Mark scheme

Mark scheme for question 5
QuestionAnswerMarkMark scheme
5
  • 1:2501 : 250
218m=1800cm18\,\text{m}=1800\,\text{cm}. The scale is 7.2:1800=1:2507.2:1800=1:250.
Q6
Tier 3 · Hard

6

A road is 9.6cm9.6\,\text{cm} long on a map with scale 1:125001:12\,500. Work out its length on a second map with scale 1:300001:30\,000.

(3)

(Total for Question 6 is 3 marks)

Mark scheme

Mark scheme for question 6
QuestionAnswerMarkMark scheme
6
  • 4cm4\,\text{cm}
3The real road length is 9.6×12500=120000cm9.6\times12\,500=120\,000\,\text{cm}. On the second map its length is 120000÷30000=4cm120\,000\div30\,000=4\,\text{cm}.
Q7
Tier 2 · Standard

7

A floor plan uses scale 1:751 : 75. A rectangular storage bay measures 6.4cm6.4\,\text{cm} by 3.6cm3.6\,\text{cm} on the plan. Work out its real perimeter in metres.

(3)

(Total for Question 7 is 3 marks)

Mark scheme

Mark scheme for question 7
QuestionAnswerMarkMark scheme
7
  • 15m15\,\text{m}
3The real dimensions are 6.4×75=480cm=4.8m6.4\times75=480\,\text{cm}=4.8\,\text{m} and 3.6×75=270cm=2.7m3.6\times75=270\,\text{cm}=2.7\,\text{m}. The perimeter is 2(4.8+2.7)=15m2(4.8+2.7)=15\,\text{m}.
Q8
Tier 3 · Hard

8

A rectangular terrace measures 9.6cm9.6\,\text{cm} by 6.4cm6.4\,\text{cm} on a plan with scale 1:1251 : 125. The terrace will be covered with square paving slabs of side 40cm40\,\text{cm}. Work out the number of slabs needed. Assume that no slabs are wasted.

(5)

(Total for Question 8 is 5 marks)

Mark scheme

Mark scheme for question 8
QuestionAnswerMarkMark scheme
8
  • 600600 slabs
5The real dimensions are 9.6×125=1200cm=12m9.6\times125=1200\,\text{cm}=12\,\text{m} and 6.4×125=800cm=8m6.4\times125=800\,\text{cm}=8\,\text{m}, so the terrace area is 96m296\,\text{m}^2. Each slab has area 0.42=0.16m20.4^2=0.16\,\text{m}^2. The number needed is 96÷0.16=60096\div0.16=600.
Q9
Tier 3 · Hard

9

A model storage tank is made to scale 1:401 : 40. The model has volume 54cm354\,\text{cm}^3. Work out the volume of the real tank in litres.

(4)

(Total for Question 9 is 4 marks)

Mark scheme

Mark scheme for question 9
QuestionAnswerMarkMark scheme
9
  • 34563456 litres
4The volume scale factor is 403=6400040^3=64\,000. The real volume is 54×64000=3456000cm354\times64\,000=3\,456\,000\,\text{cm}^3. Since 1000cm3=11000\,\text{cm}^3=1 litre, this is 34563456 litres.
Q10
Tier 3 · Hard

10

A lake covers 28.8cm228.8\,\text{cm}^2 on an aerial photograph with scale 1:80001 : 8000. Work out the area it would cover on a plan with scale 1:120001 : 12\,000.

(4)

(Total for Question 10 is 4 marks)

Mark scheme

Mark scheme for question 10
QuestionAnswerMarkMark scheme
10
  • 12.8cm212.8\,\text{cm}^2
4Lengths on the second plan are 8000÷12000=238000\div12\,000=\dfrac{2}{3} of those on the photograph. Areas are therefore multiplied by (23)2=49\left(\dfrac{2}{3}\right)^2=\dfrac{4}{9}. The area is 28.8×49=12.8cm228.8\times\dfrac{4}{9}=12.8\,\text{cm}^2.

Verified exam appearances

SeriesPaperQuestionMarksCalculatorTierLinks
2019-062FQ194AllowedFoundationQPMS
2021-112FQ52AllowedFoundationQPMS
2019-112FQ153AllowedFoundationQPMS
2019-063FQ172AllowedFoundationQPMS
2021-113FQ124AllowedFoundationQPMS
2019-111FQ275Non-calculatorFoundationQPMS
2019-111HQ85Non-calculatorHigherQPMS
2024-062HQ83AllowedHigherQPMS
2022-111FQ145Non-calculatorFoundationQPMS
2023-062FQ83AllowedFoundationQPMS
2024-112FQ153AllowedFoundationQPMS
2022-063FQ134AllowedFoundationQPMS
2022-062FQ163AllowedFoundationQPMS
2024-063FQ64AllowedFoundationQPMS
2023-113HQ113AllowedHigherQPMS
2023-111FQ72Non-calculatorFoundationQPMS

Other points in R Ratio, proportion and rates of change

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