PSLE
The number of girls and boys taking part in a test are in the ratio 7 : 4. These pupils are put into two teams. 60% of the girls and 30% of the boys are in Team D. The rest of the pupils are in Team E.

1. What is the ratio of the number of pupils in Team E to Team D? Give your answer in the simplest form.
2. The number of girls in Team E is fewer than 80. What is the largest possible total number of pupils taking part in the test?

Girls		Boys
70 u		40 u
Team D	Team E	Team D	Team E
42 u	28 u	12 u	28 u

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

Number of girls in Team D
= 60% x 70 u
= ⁶⁰₁₀₀ x 70 u
= 42 u

Number of girls in Team E
= 70 u - 42 u
= 28 u

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

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

Team E : Team D
28 + 28 : 42 + 12
56 : 54 _(÷2)
28 : 27

(b)
Number of girls in Team E = 28 u

Since the number of girls in Team E is 28 u, it must be multiple of 28.

Number of sets of 28
= 80 ÷ 28
= 2 r 24

Since the number of girls in Team E is less than 80, the number of sets must be 2.

1 u = 2

Largest possible number of pupils
= 70 u + 40 u
= 110 u
= 110 x 2
= 220

Answer(s): (a) 28 : 27; (b) 220