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 : 5. The ratio of the number of boys to girls in Group B is 5 : 1. There are 2 times as many pupils in Group B as in Group A. There are 39 more boys in Group B than Group A. What is the total number of girls?
Group A |
Group B |
12 u |
6x4 = 24 u |
Boys |
Girls |
Boys |
Girls |
7 u |
5 u |
5x4 = 20 u |
1x4 = 4 u
|
Total number of pupils in Group A
= 7 u + 5 u
= 12 u
Total number of pupils in Group B
= 2 x 12 u
= 24 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 24 and 6 is 24.
Number of more boys in Group B than Group A
= 20 u - 7 u
= 13 u
13 u = 39
1 u = 39 ÷ 13 = 3
Total number of girls
= 5 u + 4 u
= 9 u
= 9 x 3
= 27
Answer(s): 27