A stationery shop had star stickers and heart stickers in a drawer. Mei Ling took out 24 star stickers and 40% of the heart stickers. After that, the ratio of the number of star stickers to the number of heart stickers left in the drawer was 3 : 4.
- What fraction of the heart stickers was left in the drawer? Give your answer in the simplest form.
- There were 42 more heart stickers than star stickers in the drawer at first. How many star stickers were there in the drawer at first?
Need a hint?
First find what fraction of the heart stickers was left. Then change 3 : 4 into an equivalent ratio so that the heart stickers left can be split into that many equal parts.
Worked answer
- (a) Heart stickers left = 100% − 40% = 60%.
- 60% = 60/100 = 35, so 35 of the heart stickers were left.
- (b) Make the ratio bigger: star : heart left = 3 : 4 = 9 : 12. So heart left = 12 units and star left = 9 units.
- Heart left is 35 of the hearts at first, so 3 equal parts = 12 units. 1 part = 4 units, so hearts at first = 5 parts = 20 units.
- Stars at first = 9 units + 24 (the 24 taken out).
- Difference at first: 20 units − (9 units + 24) = 42, so 11 units − 24 = 42.
- 11 units = 42 + 24 = 66, so 1 unit = 6.
- Stars at first = 9 × 6 + 24 = 54 + 24 = 78.
The mistake this question tests
Percentage of a new total
Many pupils treat the 42 as the difference between the stickers left, or forget to add the 24 star stickers taken out back to the stars left. The 42 is the difference at first, before anything was taken out.
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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