PSLE
The number of girls and boys taking part in a quiz are in the ratio 7 : 5. These pupils are put into two teams. 20% of the girls and 40% of the boys are in Team J. The rest of the pupils are in Team K.

1. What is the ratio of the number of pupils in Team K to Team J? Give your answer in the simplest form.
2. The number of boys in Team J is more than 50. What is the smallest possible total number of pupils taking part in the quiz?

Girls		Boys
70 u		50 u
Team J	Team K	Team J	Team K
14 u	56 u	20 u	30 u

(a)
Girls : Boys
7 : 5
70 : 50

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

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

Number of boys in Team J
= 40% x 50 u
= ⁴⁰₁₀₀ x 50 u
= 20 u

Number of boys in Team K
= 50 u - 20 u
= 30 u

Team J : Team K
56 + 30 : 14 + 20 
86 : 34 _(÷2)
43 : 17

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

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

Number of sets of 20
= 50 ÷ 20
= 2 r 10

Since the number of boys in Team J is more than 50, the number of sets must be 1 more than 2.

1 u = 2 + 1 = 3

Smallest possible number of pupils
= 70 u + 50 u
= 120 u
= 120 x 3
= 360

Answer(s): (a) 43 : 17; (b) 360