PSLE The pupils at a school choir 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 : 2. There are 5 times as many pupils in Group B as in Group A. There are 27 more girls in Group B than Group A. What is the total number of boys?
Group A |
Group B |
4 u |
5x4 = 20 u |
Girls |
Boys |
Girls |
Boys |
3 u |
1 u |
3x4 = 12 u |
2x4 = 8 u
|
Total number of pupils in Group A
= 3 u + 1 u
= 4 u
Total number of pupils in Group B
= 5 x 4 u
= 20 u
The total number of pupils in Group B is repeated.
Use LCM to make the total number of pupils in Group B the same.
LCM of 20 and 5 is 20.
Number of more girls in Group B than Group A
= 12 u - 3 u
= 9 u
9 u = 27
1 u = 27 ÷ 9 = 3
Total number of boys
= 1 u + 8 u
= 9 u
= 9 x 3
= 27
Answer(s): 27