PSLE
The number of boys and girls taking part in a test are in the ratio 3 : 2. These pupils are put into two teams. 40% of the boys and 30% of the girls are in Team R. The rest of the pupils are in Team S.

1. What is the ratio of the number of pupils in Team S to Team R? Give your answer in the simplest form.
2. The number of girls in Team R is more than 50. What is the smallest possible total number of pupils taking part in the test?

Boys		Girls
30 u		20 u
Team R	Team S	Team R	Team S
12 u	18 u	6 u	14 u

(a)
Boys : Girls
3 : 2
30 : 20

Number of boys in Team R
= 40% x 30 u
= ⁴⁰₁₀₀ x 30 u
= 12 u

Number of boys in Team S
= 30 u - 12 u
= 18 u

Number of girls in Team R
= 30% x 20 u
= ³⁰₁₀₀ x 20 u
= 6 u

Number of girls in Team S
= 20 u - 6 u
= 14 u

Team R : Team S
18 + 14 : 12 + 6 
32 : 18 _(÷2)
16 : 9

(b)
Number of girls in Team R = 6 u

Since the number of girls in Team R is 6 u, it must be multiple of 6.

Number of sets of 6
= 50 ÷ 6
= 8 r 2

Since the number of girls in Team R is more than 50, the number of sets must be 1 more than 8.

1 u = 8 + 1 = 9

Smallest possible number of pupils
= 30 u + 20 u
= 50 u
= 50 x 9
= 450

Answer(s): (a) 16 : 9; (b) 450