PSLE The students at a sports meet are divided in Group A and Group B. The ratio of the number of girls to boys in Group A is 3 : 1. The ratio of the number of girls to boys in Group B is 9 : 1. There are 5 times as many students in Group B as in Group A. There are 105 more girls in Group B than Group A. What is the total number of boys?
Group A |
Group B |
4 u |
10x2 = 20 u |
Girls |
Boys |
Girls |
Boys |
3 u |
1 u |
9x2 = 18 u |
1x2 = 2 u
|
Total number of students in Group A
= 3 u + 1 u
= 4 u
Total number of students in Group B
= 5 x 4 u
= 20 u
The total number of students in Group B is repeated.
Use LCM to make the total number of students in Group B the same.
LCM of 20 and 10 is 20.
Number of more girls in Group B than Group A
= 18 u - 3 u
= 15 u
15 u = 105
1 u = 105 ÷ 15 = 7
Total number of boys
= 1 u + 2 u
= 3 u
= 3 x 7
= 21
Answer(s): 21