PSLE
The number of boys and girls taking part in a test are in the ratio 4 : 7. These pupils are put into two teams. 50% of the boys and 20% of the girls are in Team V. The rest of the pupils are in Team W.

1. What is the ratio of the number of pupils in Team W to Team V? Give your answer in the simplest form.
2. The number of boys in Team W is fewer than 90. What is the largest possible total number of pupils taking part in the test?

Boys		Girls
40 u		70 u
Team V	Team W	Team V	Team W
20 u	20 u	14 u	56 u

(a)
Boys : Girls
4 : 7
40 : 70

Number of boys in Team V
= 50% x 40 u
= ⁵⁰₁₀₀ x 40 u
= 20 u

Number of boys in Team W
= 40 u - 20 u
= 20 u

Number of girls in Team V
= 20% x 70 u
= ²⁰₁₀₀ x 70 u
= 14 u

Number of girls in Team W
= 70 u - 14 u
= 56 u

Team W : Team V
20 + 56 : 20 + 14
76 : 34 _(÷2)
38 : 17

(b)
Number of boys in Team W = 20 u

Since the number of boys in Team W is 20 u, it must be multiple of 20.

Number of sets of 20
= 90 ÷ 20
= 4 r 10

Since the number of boys in Team W is less than 90, the number of sets must be 4.

1 u = 4

Largest possible number of pupils
= 40 u + 70 u
= 110 u
= 110 x 4
= 440

Answer(s): (a) 38 : 17; (b) 440