Define direct proportion .

Two quantities are in direct proportion when multiplying one of them by a factor multiplies the other by the same factor . For example, if 2 boxes of cereal hold 800 g, then 4 boxes hold 1600 g.

What is the unitary method for a direct proportion problem?

Find the value for one unit first by dividing, then multiply to scale up to the amount you need. For example, if 8 boxes weigh 60 kg, one box weighs 60 ÷ 8 = 7.5 kg, so 7 boxes weigh 7.5 × 7 = 52.5 kg.

True or False? If 4 tickets cost £20, then 8 tickets cost £24.

False. The number of tickets is multiplied by 2, so the cost is multiplied by 2 as well, giving £40.

In a direct proportion problem, how do you find the factor that one quantity has been multiplied by?

Divide the new value by the old value. For example, if a bonus is £250 for every £3000 of profit, a profit of £18 000 gives a factor of 18 000 ÷ 3000 = 6, so the bonus is 250 × 6 = £1500.

True or False? In a direct proportion problem, the factor you multiply by can be less than 1.

True. If 10 litres of paint cover 40 square metres, then 4 litres is a factor of 4 ÷ 10 = 0.4, so it covers 40 × 0.4 = 16 square metres.

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Proportion (Edexcel IGCSE Maths A: Foundation): Flashcards

Exam code: 4MA1

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Define direct proportion.

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Cards in this collection (6)

Define direct proportion.
Two quantities are in direct proportion when multiplying one of them by a factor multiplies the other by the same factor.
For example, if 2 boxes of cereal hold 800 g, then 4 boxes hold 1600 g.
What is the unitary method for a direct proportion problem?
Find the value for one unit first by dividing, then multiply to scale up to the amount you need.
For example, if 8 boxes weigh 60 kg, one box weighs 60 ÷ 8 = 7.5 kg, so 7 boxes weigh 7.5 × 7 = 52.5 kg.
True or False?
If 4 tickets cost £20, then 8 tickets cost £24.
False.
The number of tickets is multiplied by 2, so the cost is multiplied by 2 as well, giving £40.
5 m of fabric costs £12. Fill in the working to find the cost, in pounds, of 15 m of the same fabric:
$12 \times______=______$
The completed working is:
$12 \times 3 = 36$
The length is multiplied by 3, so the cost is too, making it £36.
In a direct proportion problem, how do you find the factor that one quantity has been multiplied by?
Divide the new value by the old value.
For example, if a bonus is £250 for every £3000 of profit, a profit of £18 000 gives a factor of 18 000 ÷ 3000 = 6, so the bonus is 250 × 6 = £1500.
True or False?
In a direct proportion problem, the factor you multiply by can be less than 1.
True.
If 10 litres of paint cover 40 square metres, then 4 litres is a factor of 4 ÷ 10 = 0.4, so it covers 40 × 0.4 = 16 square metres.

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