PSLE
The number of girls and boys taking part in a test are in the ratio 5 : 4. These pupils are put into two teams. 60% of the girls and 30% of the boys are in Team N. The rest of the pupils are in Team P.

1. What is the ratio of the number of pupils in Team P to Team N? Give your answer in the simplest form.
2. The number of boys in Team N is more than 90. What is the smallest possible total number of pupils taking part in the test?

Girls		Boys
50 u		40 u
Team N	Team P	Team N	Team P
30 u	20 u	12 u	28 u

(a)
Girls : Boys
5 : 4
50 : 40

Number of girls in Team N
= 60% x 50 u
= ⁶⁰₁₀₀ x 50 u
= 30 u

Number of girls in Team P
= 50 u - 30 u
= 20 u

Number of boys in Team N
= 30% x 40 u
= ³⁰₁₀₀ x 40 u
= 12 u

Number of boys in Team P
= 40 u - 12 u
= 28 u

Team N : Team P
20 + 28 : 30 + 12 
48 : 42 _(÷6)
8 : 7

(b)
Number of boys in Team N = 12 u

Since the number of boys in Team N is 12 u, it must be multiple of 12.

Number of sets of 12
= 90 ÷ 12
= 7 r 6

Since the number of boys in Team N is more than 90, the number of sets must be 1 more than 7.

1 u = 7 + 1 = 8

Smallest possible number of pupils
= 50 u + 40 u
= 90 u
= 90 x 8
= 720

Answer(s): (a) 8 : 7; (b) 720