PSLE
The students at a sports meet are divided in Group A and Group B. The ratio of the number of girls to boys in Group A is 3 : 1. The ratio of the number of girls to boys in Group B is 3 : 5. There are 4 times as many students in Group B as in Group A. There are 45 more girls in Group B than Group A. What is the total number of students?

Group A		Group B
4 u		8x2 = 16 u
Girls	Boys	Girls	Boys
3 u	1 u	3x2 = 6 u	5x2 = 10 u

Total number of students in Group A
= 3 u + 1 u
= 4 u

Total number of students in Group B
= 4 x 4 u
= 16 u

The total number of students in Group B is repeated.
Use LCM to make the total number of students in Group B the same.
LCM of 16 and 8 is 16.

Number of more girls in Group B than Group A
= 6 u - 3 u
= 3 u

3 u = 45

1 u = 45 ÷ 3 = 15

Total number of students
= 3 u + 1 u + 6 u + 10 u
= 20 u
= 20 x 15
= 300

Answer(s): 300