PSLE
The number of boys and girls taking part in a contest are in the ratio 1 : 2. These pupils are put into two teams. 30% of the boys and 10% of the girls are in Team U. The rest of the pupils are in Team V.

1. What is the ratio of the number of pupils in Team V to Team U? Give your answer in the simplest form.
2. The number of boys in Team V is fewer than 50. What is the largest possible total number of pupils taking part in the contest?

Boys		Girls
10 u		20 u
Team U	Team V	Team U	Team V
3 u	7 u	2 u	18 u

(a)
Boys : Girls
1 : 2
10 : 20

Number of boys in Team U
= 30% x 10 u
= ³⁰₁₀₀ x 10 u
= 3 u

Number of boys in Team V
= 10 u - 3 u
= 7 u

Number of girls in Team U
= 10% x 20 u
= ¹⁰₁₀₀ x 20 u
= 2 u

Number of girls in Team V
= 20 u - 2 u
= 18 u

Team V : Team U
7 + 18 : 3 + 2
25 : 5 _(÷5)
5 : 1

(b)
Number of boys in Team V = 7 u

Since the number of boys in Team V is 7 u, it must be multiple of 7.

Number of sets of 7
= 50 ÷ 7
= 7 r 1

Since the number of boys in Team V is less than 50, the number of sets must be 7.

1 u = 7

Largest possible number of pupils
= 10 u + 20 u
= 30 u
= 30 x 7
= 210

Answer(s): (a) 5 : 1; (b) 210