A swimming club has 84 boys and 147 girls.
- What is the ratio of the number of boys to the number of girls in its simplest form?
- The club wants the ratio of boys to girls to be 3 : 5, keeping all 84 boys. How many girls must leave the club?
Need a hint?
For (a), find a number that divides both 84 and 147 exactly. For (b), first find how many girls go with 84 boys in the ratio 3 : 5.
Worked answer
- (a) Find the common factor of 84 and 147 that divides both: 21.
- (a) 84 ÷ 21 = 4 and 147 ÷ 21 = 7, so the ratio is 4 : 7.
- (b) With 84 boys at ratio 3 : 5, one part = 84 ÷ 3 = 28.
- (b) Girls needed = 5 × 28 = 140, so girls to leave = 147 − 140 = 7.
The mistake this question tests
Simplest form in final fraction answers
Pupils who stop at 84 : 147 or divide by a common factor like 3 only do not reach simplest form; in (b) some subtract 84 from 147 instead of working out the girls needed for the ratio.
How to fix it at home →More PSLE ratio questions
Write the ratio 12 : 18 in its simplest form
See the answer →Structured · 4mAisha, Brandon and Chen collect stamps
See the answer →Structured · 4mMei Ling overlaps a rectangular piece of red card and a circular piece of blue card on a poster
See the answer →Structured · 4mHana sticks three pieces of coloured card onto a board: a square, a circle and a triangle
See the answer →MCQ · 2mIn a class, the ratio of the number of boys to the number of girls is 3 : 4
See the answer →Short answer · 2mA school trip has 240 Primary 5 pupils and 360 Primary 6 pupils
See the answer →Practise PSLE ratio until the mistakes stop.
Three PSLE questions, free, no sign-up. You’ll see exactly where the marks went. Then 7 days of everything for S$4.99.