PSLE
The contestants at a contest 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 2 : 1. There are 3 times as many contestants in Team B as in Team A. There are 42 less boys in Team A than Team B. What is the total number of contestants in Team A?

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

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

Total number of contestants in Team B
= 3 x 5 u
= 15 u

The total number of contestants in Team B is repeated.
Use LCM to make the total number of contestants in Team B the same.
LCM of 15 and 3 is 15.

Number of less boys in Team A than Team B
= 10 u - 4 u
= 6 u

6 u = 42

1 u = 42 ÷ 6 = 7

Total number of contestants in Team A
= 4 u + 1 u
= 5 u
= 5 x 7
= 35

Answer(s): 35