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R7

Understand and use proportion as equality of ratios

Proportion

Worked answers, methods and verified real exam appearances for R7 on Edexcel GCSE Maths 1MA1.

Explanation

  • Proportion means that two corresponding ratios are equal. Keep the quantities in the same order on both sides, then solve by scaling, finding a unit value, or cross-multiplying.
  • If ab=cd\dfrac{a}{b}=\dfrac{c}{d} with non-zero denominators, then ad=bcad=bc.
  • A unitary method is often clearest in context: find the amount for one unit and scale to the required number.
  • Decimal answers involving money must be interpreted in pounds and pence.
  • Examiners award method for a correct proportional relationship even if a later arithmetic slip occurs, so show the equation or unit value.

Worked example

Eight identical notebooks cost £11.20. Use proportion to find the cost of 1414 notebooks.

  1. 1.Find the cost of one notebook: 11.20÷8=1.4011.20\div8=1.40.
  2. 2.Scale to 1414 notebooks: 14×1.40=19.6014\times1.40=19.60.
  3. 3.State the money answer using two decimal places.

Answer: £19.60.

Common mistakes

  • Don't place corresponding quantities in different orders in the two ratios.
  • Don't add the same amount instead of multiplying by the same scale factor.
  • Don't write £19.6 without interpreting the final zero as pence in a money context.

Exam tip

Show either the equal-ratios equation or the value of one unit before giving the scaled answer.

Worked practice

Q1
Tier 1 · Easy

1

Solve the proportion x15=610\frac{x}{15}=\frac{6}{10}.

(2)

(Total for Question 1 is 2 marks)

Mark scheme

Mark scheme for question 1
QuestionAnswerMarkMark scheme
1
  • x=9x=9
2x=15×610=9x=15\times\frac{6}{10}=9.
Q2
Tier 2 · Standard

2

A recipe uses 180180 g of flour for every 120120 g of sugar. Leo uses 315315 g of flour and 200200 g of sugar. Has Leo used flour and sugar in the correct proportion? Show your working.

(3)

(Total for Question 2 is 3 marks)

Mark scheme

Mark scheme for question 2
QuestionAnswerMarkMark scheme
2
  • No, because 180:120=3:2180:120=3:2 but 315:200=63:40315:200=63:40.
3Simplify the recipe ratio to 180:120=3:2180:120=3:2. Leo's ratio is 315:200=63:40315:200=63:40, which is not equal to 3:23:2, so the ingredients are not in the correct proportion.
Q3
Tier 3 · Hard

3

Solve 2x+318=x+612\frac{2x+3}{18}=\frac{x+6}{12} and verify that the two ratios are equal.

(4)

(Total for Question 3 is 4 marks)

Mark scheme

Mark scheme for question 3
QuestionAnswerMarkMark scheme
3
  • x=12x=12
  • Both ratios equal 32\frac{3}{2}
4Cross-multiply: 12(2x+3)=18(x+6)12(2x+3)=18(x+6). This gives 24x+36=18x+10824x+36=18x+108, so 6x=726x=72 and x=12x=12. Substitution gives 27/18=18/12=3/227/18=18/12=3/2.
Q4
Tier 1 · Easy

4

Which ratio is equal to 5:85:8? A 10:1810:18 B 15:2415:24 C 20:3020:30. Write down the letter of the correct ratio.

(1)

(Total for Question 4 is 1 mark)

Mark scheme

Mark scheme for question 4
QuestionAnswerMarkMark scheme
4
  • B
115:2415:24 simplifies to 5:85:8 after dividing both parts by 33, so the correct letter is B.
Q5
Tier 2 · Standard

5

A photograph has width to height ratio 7:47:4. Work out its width when its height is 18cm18\,\text{cm}.

(2)

(Total for Question 5 is 2 marks)

Mark scheme

Mark scheme for question 5
QuestionAnswerMarkMark scheme
5
  • 31.5cm31.5\,\text{cm}
2The scale factor from 44 to 1818 is 18÷4=4.518\div4=4.5. The width is 7×4.5=31.5cm7\times4.5=31.5\,\text{cm}.
Q6
Tier 3 · Hard

6

A printer produces 126126 pages in 3.53.5 minutes at a constant rate. Work out how long it takes to produce 270270 pages.

(3)

(Total for Question 6 is 3 marks)

Mark scheme

Mark scheme for question 6
QuestionAnswerMarkMark scheme
6
  • 7.57.5 minutes
3The printer produces 126÷3.5=36126\div3.5=36 pages per minute. The time for 270270 pages is 270÷36=7.5270\div36=7.5 minutes.
Q7
Tier 2 · Standard

7

Nine identical bolts have a total mass of 234g234\,\text{g}. Work out the total mass of 1414 of these bolts.

(2)

(Total for Question 7 is 2 marks)

Mark scheme

Mark scheme for question 7
QuestionAnswerMarkMark scheme
7
  • 364g364\,\text{g}
2One bolt has mass 234÷9=26g234\div9=26\,\text{g}. Therefore 1414 bolts have mass 14×26=364g14\times26=364\,\text{g}.
Q8
Tier 3 · Hard

8

A fruit drink contains syrup and water in the ratio 3:83 : 8. After 1.51.5 litres of water evaporates, the ratio is 3:73 : 7. Work out the original volume of the drink.

(4)

(Total for Question 8 is 4 marks)

Mark scheme

Mark scheme for question 8
QuestionAnswerMarkMark scheme
8
  • 16.516.5 litres
4Let the original amounts be 3k3k and 8k8k litres. Equality of the new ratios gives 3k8k1.5=37\dfrac{3k}{8k-1.5}=\dfrac{3}{7}. Hence 21k=24k4.521k=24k-4.5, so k=1.5k=1.5. The original volume was 11k=16.511k=16.5 litres.
Q9
Tier 3 · Hard

9

A photograph is 24cm24\,\text{cm} wide and 16cm16\,\text{cm} high. A strip of width xcmx\,\text{cm} is cut from both the left edge and the right edge. The new width and height are in the ratio 4:34 : 3. Work out xx.

(4)

(Total for Question 9 is 4 marks)

Mark scheme

Mark scheme for question 9
QuestionAnswerMarkMark scheme
9
  • x=43cmx=\dfrac{4}{3}\,\text{cm}
4The new width is 242x24-2x. Equality of the ratios gives 242x16=43\dfrac{24-2x}{16}=\dfrac{4}{3}. Hence 726x=6472-6x=64, so 6x=86x=8 and x=43cmx=\dfrac{4}{3}\,\text{cm}.
Q10
Tier 3 · Hard

10

A recipe uses 400g400\,\text{g} of toasted oats to make 1414 snack bars. During toasting, oats lose 4%4\% of their mass. Work out the greatest number of complete snack bars that can be made from 1.875kg1.875\,\text{kg} of untoasted oats.

(4)

(Total for Question 10 is 4 marks)

Mark scheme

Mark scheme for question 10
QuestionAnswerMarkMark scheme
10
  • 6363 complete snack bars
41.875kg=1875g1.875\,\text{kg}=1875\,\text{g}. After toasting, 1875×0.96=1800g1875\times0.96=1800\,\text{g} remains. Since 1800÷400=4.51800\div400=4.5 recipe batches, the number of bars is 4.5×14=634.5\times14=63.

Verified exam appearances

SeriesPaperQuestionMarksCalculatorTierLinks
2019-112FQ243AllowedFoundationQPMS
2022-112HQ154AllowedHigherQPMS
2023-062HQ183AllowedHigherQPMS
2024-113HQ184AllowedHigherQPMS
2022-062HQ143AllowedHigherQPMS
2019-061HQ174Non-calculatorHigherQPMS

Other points in R Ratio, proportion and rates of change

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