PSLE
The pupils at a camp are divided in Group A and Group B. The ratio of the number of boys to girls in Group A is 3 : 1. The ratio of the number of boys to girls in Group B is 2 : 3. There are 5 times as many pupils in Group B as in Group A. There are 25 more boys in Group B than Group A. What is the total number of pupils?

Group A		Group B
4 u		5x4 = 20 u
Boys	Girls	Boys	Girls
3 u	1 u	2x4 = 8 u	3x4 = 12 u

Total number of pupils in Group A
= 3 u + 1 u
= 4 u

Total number of pupils in Group B
= 5 x 4 u
= 20 u

The total number of pupils in Group B is repeated.
Use LCM to make the total number of pupils in Group B the same.
LCM of 20 and 5 is 20.

Number of more boys in Group B than Group A
= 8 u - 3 u
= 5 u

5 u = 25

1 u = 25 ÷ 5 = 5

Total number of pupils
= 3 u + 1 u + 8 u + 12 u
= 24 u
= 24 x 5
= 120

Answer(s): 120