65 pupils from Class W and Class X took a Mathematics test. The average marks of the pupils was 85 marks. The average marks of the pupils in Class W was 91 marks and the average marks of the pupils in Class X was 76 marks. How many pupils were there in Class W?
Pupils in
Class W |
Total scores in
Class W |
Pupils in
Class X |
Total scores in
Class X |
Total scores of
Class W and Class X |
65
|
65 x 91 =
5915 |
0
|
0
|
5915
|
64
|
64 x 91 =
5824 |
1
|
1 x 76 =
76 |
5900
|
39
|
39 x 91 =
3549 |
26
|
26 x 76 =
1976 |
5525
|
Total scores of Class X and Class W
= 65 x 85
= 5525
If all the pupils are in Class W,
total scores
= 65 x 91
= 5915
Big difference
= 5915 - 5525
= 390
Small difference
= 91 - 76
= 15
Number of pupils in Class X
= 390 ÷ 15
= 26
Number of pupils in Class W
= 65 - 26
= 39
Answer(s): 39
