PSLE
The number of girls and boys taking part in a test are in the ratio 2 : 7. These students are put into two teams. 60% of the girls and 30% of the boys are in Team U. The rest of the students are in Team V.

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

Girls		Boys
20 u		70 u
Team U	Team V	Team U	Team V
12 u	8 u	21 u	49 u

(a)
Girls : Boys
2 : 7
20 : 70

Number of girls in Team U
= 60% x 20 u
= ⁶⁰₁₀₀ x 20 u
= 12 u

Number of girls in Team V
= 20 u - 12 u
= 8 u

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

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

Team U : Team V
8 + 49 : 12 + 21 
57 : 33 _(÷3)
19 : 11

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

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

1 u = 4 + 1 = 5

Smallest possible number of students
= 20 u + 70 u
= 90 u
= 90 x 5
= 450

Answer(s): (a) 19 : 11; (b) 450