PSLE
The number of boys and girls taking part in a contest are in the ratio 5 : 4. These pupils are put into two teams. 70% of the boys and 10% of the girls are in Team L. The rest of the pupils are in Team M.

1. What is the ratio of the number of pupils in Team M to Team L? Give your answer in the simplest form.
2. The number of boys in Team M is fewer than 40. What is the largest possible total number of pupils taking part in the contest?

Boys		Girls
50 u		40 u
Team L	Team M	Team L	Team M
35 u	15 u	4 u	36 u

(a)
Boys : Girls
5 : 4
50 : 40

Number of boys in Team L
= 70% x 50 u
= ⁷⁰₁₀₀ x 50 u
= 35 u

Number of boys in Team M
= 50 u - 35 u
= 15 u

Number of girls in Team L
= 10% x 40 u
= ¹⁰₁₀₀ x 40 u
= 4 u

Number of girls in Team M
= 40 u - 4 u
= 36 u

Team M : Team L
15 + 36 : 35 + 4
51 : 39 _(÷3)
17 : 13

(b)
Number of boys in Team M = 15 u

Since the number of boys in Team M is 15 u, it must be multiple of 15.

Number of sets of 15
= 40 ÷ 15
= 2 r 10

Since the number of boys in Team M is less than 40, the number of sets must be 2.

1 u = 2

Largest possible number of pupils
= 50 u + 40 u
= 90 u
= 90 x 2
= 180

Answer(s): (a) 17 : 13; (b) 180