75 pupils from Class U and Class V took a Mathematics test. The average marks of the pupils was 86 marks. The average marks of the pupils in Class U was 91 marks and the average marks of the pupils in Class V was 76 marks. How many pupils were there in Class U?
Pupils in
Class U |
Total scores in
Class U |
Pupils in
Class V |
Total scores in
Class V |
Total scores of
Class U and Class V |
75
|
75 x 91 =
6825 |
0
|
0
|
6825
|
74
|
74 x 91 =
6734 |
1
|
1 x 76 =
76 |
6810
|
50
|
50 x 91 =
4550 |
25
|
25 x 76 =
1900 |
6450
|
Total scores of Class V and Class U
= 75 x 86
= 6450
If all the pupils are in Class U,
total scores
= 75 x 91
= 6825
Big difference
= 6825 - 6450
= 375
Small difference
= 91 - 76
= 15
Number of pupils in Class V
= 375 ÷ 15
= 25
Number of pupils in Class U
= 75 - 25
= 50
Answer(s): 50
