At a swimming gala, the number of boys was 20% more than the number of girls. There were 264 pupils altogether.
- Let the number of girls be 5 units. How many units is the number of boys? (1 mark)
- How many units are there altogether, and what is the value of one unit? (1 mark)
- How many girls were there at the gala? (1 mark)
Need a hint?
The 20% is taken on the number of girls, not on the total of 264. Count how many units the boys are compared with the girls first.
Worked answer
- (a) 20% more than 5 units means 5 units + 1 unit, so the boys are 6 units.
- (b) Girls and boys together are 5 + 6 = 11 units. So one unit is 264 ÷ 11 = 24 pupils.
- (c) Girls are 5 units, so 5 × 24 = 120 girls.
Answer: 120 pupils
The mistake this question tests
Habit
Found the increase, not the new price
Pupils often take 20% of 264 (52.8) and subtract or add it, which treats the 264 as the girls' number. The 20% increase is always based on the smaller group (the girls).
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See the answer →Practise PSLE percentage until the mistakes stop.
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