At a night market, Stall X sold 23 of its keychains, Stall Y sold 14 of its keychains and Stall Z sold 12 of its keychains. Each stall sold the same number of keychains.
- What fraction of all the keychains were sold?
- The three stalls had 585 keychains at first. How many keychains did Stall Y have at first?
Need a hint?
The number sold is the same for every stall. Call it 6 units, then work out how many units each stall had at first.
Worked answer
- (a) Let the number of keychains each stall sold be 6 units.
- 23 of Stall X = 6 units, so 13 = 3 units and Stall X had 9 units at first.
- 14 of Stall Y = 6 units, so Stall Y had 6 × 4 = 24 units at first.
- 12 of Stall Z = 6 units, so Stall Z had 6 × 2 = 12 units at first.
- All three stalls at first: 9 + 24 + 12 = 45 units. Sold: 6 + 6 + 6 = 18 units.
- Fraction sold = 18 ÷ 45 = 25.
- (b) 45 units = 585, so 1 unit = 585 ÷ 45 = 13.
- Stall Y had 24 units = 24 × 13 = 312 keychains at first.
The mistake this question tests
Stopped at one part in ratio
Many pupils add 23 + 14 + 12 as if the three stalls had the same total. But the stalls started with different numbers of keychains, so the fractions cannot be added directly.
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See the answer →Practise PSLE fractions until the mistakes stop.
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