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 4 : 3. The ratio of the number of girls to boys in Group B is 5 : 9. There are 4 times as many pupils in Group B as in Group A. There are 12 more girls in Group B than Group A. What is the total number of boys?
Group A |
Group B |
7 u |
14x2 = 28 u |
Girls |
Boys |
Girls |
Boys |
4 u |
3 u |
5x2 = 10 u |
9x2 = 18 u
|
Total number of pupils in Group A
= 4 u + 3 u
= 7 u
Total number of pupils in Group B
= 4 x 7 u
= 28 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 28 and 14 is 28.
Number of more girls in Group B than Group A
= 10 u - 4 u
= 6 u
6 u = 12
1 u = 12 ÷ 6 = 2
Total number of boys
= 3 u + 18 u
= 21 u
= 21 x 2
= 42
Answer(s): 42