75 pupils from Class P and Class Q took a Mathematics test. The average marks of the pupils was 81 marks. The average marks of the pupils in Class P was 83 marks and the average marks of the pupils in Class Q was 77 marks. How many pupils were there in Class P?
Pupils in
Class P |
Total scores in
Class P |
Pupils in
Class Q |
Total scores in
Class Q |
Total scores of
Class P and Class Q |
75
|
75 x 83 =
6225 |
0
|
0
|
6225
|
74
|
74 x 83 =
6142 |
1
|
1 x 77 =
77 |
6219
|
50
|
50 x 83 =
4150 |
25
|
25 x 77 =
1925 |
6075
|
Total scores of Class Q and Class P
= 75 x 81
= 6075
If all the pupils are in Class P,
total scores
= 75 x 83
= 6225
Big difference
= 6225 - 6075
= 150
Small difference
= 83 - 77
= 6
Number of pupils in Class Q
= 150 ÷ 6
= 25
Number of pupils in Class P
= 75 - 25
= 50
Answer(s): 50
