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 3 : 2. The ratio of the number of boys to girls in Group B is 3 : 1. There are 4 times as many pupils in Group B as in Group A. There are 120 more boys in Group B than Group A. What is the total number of girls?
Group A |
Group B |
5 u |
4x5 = 20 u |
Boys |
Girls |
Boys |
Girls |
3 u |
2 u |
3x5 = 15 u |
1x5 = 5 u
|
Total number of pupils in Group A
= 3 u + 2 u
= 5 u
Total number of pupils in Group B
= 4 x 5 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 4 is 20.
Number of more boys in Group B than Group A
= 15 u - 3 u
= 12 u
12 u = 120
1 u = 120 ÷ 12 = 10
Total number of girls
= 2 u + 5 u
= 7 u
= 7 x 10
= 70
Answer(s): 70