PSLE
The students at a sports meet 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 4 : 1. There are 2 times as many students in Team B as in Team A. There are 81 more girls in Team B than Team A. What is the total number of students?

Team A		Team B
10 u		5x4 = 20 u
Girls	Boys	Girls	Boys
7 u	3 u	4x4 = 16 u	1x4 = 4 u

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

Total number of students in Team B
= 2 x 10 u
= 20 u

The total number of students in Team B is repeated.
Use LCM to make the total number of students in Team B the same.
LCM of 20 and 5 is 20.

Number of more girls in Team B than Team A
= 16 u - 7 u
= 9 u

9 u = 81

1 u = 81 ÷ 9 = 9

Total number of students
= 7 u + 3 u + 16 u + 4 u
= 30 u
= 30 x 9
= 270

Answer(s): 270