The average number of boys in 5A, 5B and 5C is 20. This is 4 more than the average number of girls in the 3 rooms.
38 of the total number of girls are in 5C.
32 of the number of girls in 5B is the same as
38 of the total number of girls in the 3 rooms. What fraction of the total number of boys in the 3 rooms is in 5A if there are 36 pupils in 5A?
| Girls in 5A |
Girls in 5B |
Girls in 5C |
Total girls |
| 5 |
3 |
8 |
| |
2 |
|
8 |
| 3 u |
2 u |
3 u |
8 u |
32 of girls in 5B =
38 of all girls
Girls in 5B : All girls = 2 : 8
Average number of girls
= 20 - 4
= 16
Total number of girls
= 3 x 16
= 48
8 u = 48
1 u = 48 ÷ 8 = 6
Number of girls in Room 5A
= 3 u
= 3 x 6
= 18
Number of boys in Room 5A
= 36 - 18
= 18
Total number of boys
= 3 x 20
= 60
Boys in 5ATotal boys =
1860 =
310 Answer(s):
310 
