PSLE
The number of girls and boys taking part in a contest are in the ratio 1 : 5. These students are put into two teams. 10% of the girls and 30% of the boys are in Team J. The rest of the students are in Team K.

1. What is the ratio of the number of students in Team K to Team J? Give your answer in the simplest form.
2. The number of girls in Team K is fewer than 70. What is the largest possible total number of students taking part in the contest?

Girls		Boys
10 u		50 u
Team J	Team K	Team J	Team K
1 u	9 u	15 u	35 u

(a)
Girls : Boys
1 : 5
10 : 50

Number of girls in Team J
= 10% x 10 u
= ¹⁰₁₀₀ x 10 u
= 1 u

Number of girls in Team K
= 10 u - 1 u
= 9 u

Number of boys in Team J
= 30% x 50 u
= ³⁰₁₀₀ x 50 u
= 15 u

Number of boys in Team K
= 50 u - 15 u
= 35 u

Team K : Team J
9 + 35 : 1 + 15
44 : 16 _(÷4)
11 : 4

(b)
Number of girls in Team K = 9 u

Since the number of girls in Team K is 9 u, it must be multiple of 9.

Number of sets of 9
= 70 ÷ 9
= 7 r 7

Since the number of girls in Team K is less than 70, the number of sets must be 7.

1 u = 7

Largest possible number of students
= 10 u + 50 u
= 60 u
= 60 x 7
= 420

Answer(s): (a) 11 : 4; (b) 420