Aisha, Brandon and Chen collect stamps. The ratio of Aisha's number of stamps to Brandon's number of stamps is 3 : 8. The ratio of Chen's number of stamps to Aisha's number of stamps is 2 : 5.
- What fraction of Brandon's number of stamps is Chen's number of stamps? Give your answer in the simplest form.
- Brandon has 68 more stamps than Chen. How many stamps does Aisha have?
Need a hint?
Aisha appears in both ratios. Change the ratios so that Aisha has the same number of units in each one.
Worked answer
- Aisha is in both ratios, so make her share the same. 3 and 5 both go into 15.
- Aisha : Brandon = 3 : 8 = 15 : 40.
- Chen : Aisha = 2 : 5 = 6 : 15.
- So Chen : Aisha : Brandon = 6 : 15 : 40.
- (a) Chen is 6 units and Brandon is 40 units, so Chen's stamps are 640 of Brandon's.
- 640 in simplest form is 320.
- (b) Brandon − Chen = 40 − 6 = 34 units.
- 34 units = 68, so 1 unit = 68 ÷ 34 = 2.
- Aisha has 15 units: 15 × 2 = 30 stamps.
The mistake this question tests
Simplest form in final fraction answers
Many pupils join the ratios without matching Aisha's share, for example writing 2 : 3 : 8. Aisha has 3 units in one ratio and 5 units in the other, so these must be made equal first.
How to fix it at home →More PSLE ratio questions
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See the answer →Practise PSLE ratio until the mistakes stop.
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