PSLE
The number of boys and girls taking part in a contest are in the ratio 3 : 4. These pupils are put into two teams. 80% of the boys and 20% of the girls are in Team W. The rest of the pupils are in Team X.

1. What is the ratio of the number of pupils in Team X to Team W? Give your answer in the simplest form.
2. The number of girls in Team W is more than 70. What is the smallest possible total number of pupils taking part in the contest?

Boys		Girls
30 u		40 u
Team W	Team X	Team W	Team X
24 u	6 u	8 u	32 u

(a)
Boys : Girls
3 : 4
30 : 40

Number of boys in Team W
= 80% x 30 u
= ⁸⁰₁₀₀ x 30 u
= 24 u

Number of boys in Team X
= 30 u - 24 u
= 6 u

Number of girls in Team W
= 20% x 40 u
= ²⁰₁₀₀ x 40 u
= 8 u

Number of girls in Team X
= 40 u - 8 u
= 32 u

Team W : Team X
6 + 32 : 24 + 8 
38 : 32 _(÷2)
19 : 16

(b)
Number of girls in Team W = 8 u

Since the number of girls in Team W is 8 u, it must be multiple of 8.

Number of sets of 8
= 70 ÷ 8
= 8 r 6

Since the number of girls in Team W is more than 70, the number of sets must be 1 more than 8.

1 u = 8 + 1 = 9

Smallest possible number of pupils
= 30 u + 40 u
= 70 u
= 70 x 9
= 630

Answer(s): (a) 19 : 16; (b) 630