PSLE
The contestants at a contest are divided in Group A and Group B. The ratio of the number of girls to boys in Group A is 2 : 1. The ratio of the number of girls to boys in Group B is 2 : 3. There are 5 times as many contestants in Group B as in Group A. There are 8 more girls in Group B than Group A. What is the total number of boys?

Group A		Group B
3 u		5x3 = 15 u
Girls	Boys	Girls	Boys
2 u	1 u	2x3 = 6 u	3x3 = 9 u

Total number of contestants in Group A
= 2 u + 1 u
= 3 u

Total number of contestants in Group B
= 5 x 3 u
= 15 u

The total number of contestants in Group B is repeated.
Use LCM to make the total number of contestants in Group B the same.
LCM of 15 and 5 is 15.

Number of more girls in Group B than Group A
= 6 u - 2 u
= 4 u

4 u = 8

1 u = 8 ÷ 4 = 2

Total number of boys
= 1 u + 9 u
= 10 u
= 10 x 2
= 20

Answer(s): 20