PSLE
The pupils at a camp are divided in Team A and Team B. The ratio of the number of boys to girls in Team A is 7 : 3. The ratio of the number of boys to girls in Team B is 11 : 4. There are 3 times as many pupils in Team B as in Team A. There are 90 more boys in Team B than Team A. What is the total number of girls?

Team A		Team B
10 u		15x2 = 30 u
Boys	Girls	Boys	Girls
7 u	3 u	11x2 = 22 u	4x2 = 8 u

Total number of pupils in Team A
= 7 u + 3 u
= 10 u

Total number of pupils in Team B
= 3 x 10 u
= 30 u

The total number of pupils in Team B is repeated.
Use LCM to make the total number of pupils in Team B the same.
LCM of 30 and 15 is 30.

Number of more boys in Team B than Team A
= 22 u - 7 u
= 15 u

15 u = 90

1 u = 90 ÷ 15 = 6

Total number of girls
= 3 u + 8 u
= 11 u
= 11 x 6
= 66

Answer(s): 66