PSLE The pupils at a school choir are divided in Group A and Group B. The ratio of the number of boys to girls in Group A is 2 : 1. The ratio of the number of boys to girls in Group B is 4 : 1. There are 5 times as many pupils in Group B as in Group A. There are 80 less boys in Group A than Group B. What is the total number of pupils in Group A?
Group A |
Group B |
3 u |
5x3 = 15 u |
Boys |
Girls |
Boys |
Girls |
2 u |
1 u |
4x3 = 12 u |
1x3 = 3 u
|
Total number of pupils in Group A
= 2 u + 1 u
= 3 u
Total number of pupils in Group B
= 5 x 3 u
= 15 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 15 and 5 is 15.
Number of less boys in Group A than Group B
= 12 u - 2 u
= 10 u
10 u = 80
1 u = 80 ÷ 10 = 8
Total number of pupils in Group A
= 2 u + 1 u
= 3 u
= 3 x 8
= 24
Answer(s): 24