PSLE
The number of girls and boys taking part in a test are in the ratio 1 : 7. These students are put into two teams. 50% of the girls and 10% of the boys are in Team W. The rest of the students are in Team X.

1. What is the ratio of the number of students in Team X to Team W? Give your answer in the simplest form.
2. The number of boys in Team W is more than 80. What is the smallest possible total number of students taking part in the test?

Girls		Boys
10 u		70 u
Team W	Team X	Team W	Team X
5 u	5 u	7 u	63 u

(a)
Girls : Boys
1 : 7
10 : 70

Number of girls in Team W
= 50% x 10 u
= ⁵⁰₁₀₀ x 10 u
= 5 u

Number of girls in Team X
= 10 u - 5 u
= 5 u

Number of boys in Team W
= 10% x 70 u
= ¹⁰₁₀₀ x 70 u
= 7 u

Number of boys in Team X
= 70 u - 7 u
= 63 u

Team W : Team X
5 + 63 : 5 + 7 
68 : 12 _(÷4)
17 : 3

(b)
Number of boys in Team W = 7 u

Since the number of boys in Team W is 7 u, it must be multiple of 7.

Number of sets of 7
= 80 ÷ 7
= 11 r 3

Since the number of boys in Team W is more than 80, the number of sets must be 1 more than 11.

1 u = 11 + 1 = 12

Smallest possible number of students
= 10 u + 70 u
= 80 u
= 80 x 12
= 960

Answer(s): (a) 17 : 3; (b) 960