50 pupils from Class L and Class M took a Mathematics test. The average marks of the pupils was 77 marks. The average marks of the pupils in Class L was 81 marks and the average marks of the pupils in Class M was 76 marks. How many pupils were there in Class L?
Pupils in
Class L |
Total scores in
Class L |
Pupils in
Class M |
Total scores in
Class M |
Total scores of
Class L and Class M |
50
|
50 x 81 =
4050 |
0
|
0
|
4050
|
49
|
49 x 81 =
3969 |
1
|
1 x 76 =
76 |
4045
|
10
|
10 x 81 =
810 |
40
|
40 x 76 =
3040 |
3850
|
Total scores of Class M and Class L
= 50 x 77
= 3850
If all the pupils are in Class L,
total scores
= 50 x 81
= 4050
Big difference
= 4050 - 3850
= 200
Small difference
= 81 - 76
= 5
Number of pupils in Class M
= 200 ÷ 5
= 40
Number of pupils in Class L
= 50 - 40
= 10
Answer(s): 10
