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 : 2. The ratio of the number of boys to girls in Group B is 1 : 2. There are 3 times as many pupils in Group B as in Group A. There are 10 less boys in Group A than Group B. What is the total number of pupils in Group A?

Group A		Group B
5 u		3x5 = 15 u
Boys	Girls	Boys	Girls
3 u	2 u	1x5 = 5 u	2x5 = 10 u

Total number of pupils in Group A
= 3 u + 2 u
= 5 u

Total number of pupils in Group B
= 3 x 5 u
= 15 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 15 and 3 is 15.

Number of less boys in Group A than Group B
= 5 u - 3 u
= 2 u

2 u = 10

1 u = 10 ÷ 2 = 5

Total number of pupils in Group A
= 3 u + 2 u
= 5 u
= 5 x 5
= 25

Answer(s): 25