The average number of boys in 2A, 2B and 2C is 15. This is 2 more than the average number of girls in the 3 rooms.
113 of the total number of girls are in 2C.
32 of the number of girls in 2B is the same as
313 of the total number of girls in the 3 rooms. What fraction of the total number of boys in the 3 rooms is in 2A if there are 45 pupils in 2A?
| Girls in 2A |
Girls in 2B |
Girls in 2C |
Total girls |
| 12 |
1 |
13 |
| |
2 |
|
13 |
| 10 u |
2 u |
1 u |
13 u |
32 of girls in 2B =
313 of all girls
Girls in 2B : All girls = 2 : 13
Average number of girls
= 15 - 2
= 13
Total number of girls
= 3 x 13
= 39
13 u = 39
1 u = 39 ÷ 13 = 3
Number of girls in Room 2A
= 10 u
= 10 x 3
= 30
Number of boys in Room 2A
= 45 - 30
= 15
Total number of boys
= 3 x 15
= 45
Boys in 2ATotal boys =
1545 =
13 Answer(s):
13 
