PSLE
The pupils at a camp are divided in Team A and Team B. The ratio of the number of girls to boys in Team A is 7 : 3. The ratio of the number of girls to boys in Team B is 5 : 1. There are 3 times as many pupils in Team B as in Team A. There are 180 less girls in Team A than Team B. What is the total number of pupils in Team A?

Team A		Team B
10 u		6x5 = 30 u
Girls	Boys	Girls	Boys
7 u	3 u	5x5 = 25 u	1x5 = 5 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 6 is 30.

Number of less girls in Team A than Team B
= 25 u - 7 u
= 18 u

18 u = 180

1 u = 180 ÷ 18 = 10

Total number of pupils in Team A
= 7 u + 3 u
= 10 u
= 10 x 10
= 100

Answer(s): 100