PSLE
The number of girls and boys taking part in a test are in the ratio 7 : 8. These pupils are put into two teams. 70% of the girls and 10% of the boys are in Team S. The rest of the pupils are in Team T.

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

Girls		Boys
70 u		80 u
Team S	Team T	Team S	Team T
49 u	21 u	8 u	72 u

(a)
Girls : Boys
7 : 8
70 : 80

Number of girls in Team S
= 70% x 70 u
= ⁷⁰₁₀₀ x 70 u
= 49 u

Number of girls in Team T
= 70 u - 49 u
= 21 u

Number of boys in Team S
= 10% x 80 u
= ¹⁰₁₀₀ x 80 u
= 8 u

Number of boys in Team T
= 80 u - 8 u
= 72 u

Team T : Team S
21 + 72 : 49 + 8
93 : 57 _(÷3)
31 : 19

(b)
Number of girls in Team T = 21 u

Since the number of girls in Team T is 21 u, it must be multiple of 21.

Number of sets of 21
= 90 ÷ 21
= 4 r 6

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

1 u = 4

Largest possible number of pupils
= 70 u + 80 u
= 150 u
= 150 x 4
= 600

Answer(s): (a) 31 : 19; (b) 600