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 4 : 1. The ratio of the number of boys to girls in Team B is 3 : 1. There are 4 times as many pupils in Team B as in Team A. There are 66 less boys in Team A than Team B. What is the total number of pupils in Team A?

Team A		Team B
5 u		4x5 = 20 u
Boys	Girls	Boys	Girls
4 u	1 u	3x5 = 15 u	1x5 = 5 u

Total number of pupils in Team A
= 4 u + 1 u
= 5 u

Total number of pupils in Team B
= 4 x 5 u
= 20 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 20 and 4 is 20.

Number of less boys in Team A than Team B
= 15 u - 4 u
= 11 u

11 u = 66

1 u = 66 ÷ 11 = 6

Total number of pupils in Team A
= 4 u + 1 u
= 5 u
= 5 x 6
= 30

Answer(s): 30