PSLE
The number of girls and boys taking part in a contest are in the ratio 4 : 7. These students are put into two teams. 60% of the girls and 30% of the boys are in Team B. The rest of the students are in Team C.

1. What is the ratio of the number of students in Team C to Team B? Give your answer in the simplest form.
2. The number of boys in Team B is more than 90. What is the smallest possible total number of students taking part in the contest?

Girls		Boys
40 u		70 u
Team B	Team C	Team B	Team C
24 u	16 u	21 u	49 u

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

Number of girls in Team B
= 60% x 40 u
= ⁶⁰₁₀₀ x 40 u
= 24 u

Number of girls in Team C
= 40 u - 24 u
= 16 u

Number of boys in Team B
= 30% x 70 u
= ³⁰₁₀₀ x 70 u
= 21 u

Number of boys in Team C
= 70 u - 21 u
= 49 u

Team B : Team C
16 + 49 : 24 + 21 
65 : 45 _(÷5)
13 : 9

(b)
Number of boys in Team B = 21 u

Since the number of boys in Team B is 21 u, it must be multiple of 21.

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

Since the number of boys in Team B is more than 90, the number of sets must be 1 more than 4.

1 u = 4 + 1 = 5

Smallest possible number of students
= 40 u + 70 u
= 110 u
= 110 x 5
= 550

Answer(s): (a) 13 : 9; (b) 550