PSLE The pupils at a camp are divided in Group A and Group B. The ratio of the number of boys to girls in Group A is 7 : 3. The ratio of the number of boys to girls in Group B is 5 : 1. There are 3 times as many pupils in Group B as in Group A. There are 36 more boys in Group B than Group A. What is the total number of girls?
Group A |
Group B |
10 u |
6x5 = 30 u |
Boys |
Girls |
Boys |
Girls |
7 u |
3 u |
5x5 = 25 u |
1x5 = 5 u
|
Total number of pupils in Group A
= 7 u + 3 u
= 10 u
Total number of pupils in Group B
= 3 x 10 u
= 30 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 30 and 6 is 30.
Number of more boys in Group B than Group A
= 25 u - 7 u
= 18 u
18 u = 36
1 u = 36 ÷ 18 = 2
Total number of girls
= 3 u + 5 u
= 8 u
= 8 x 2
= 16
Answer(s): 16