50 pupils from Class P and Class Q took a Mathematics test. The average marks of the pupils was 84 marks. The average marks of the pupils in Class P was 87 marks and the average marks of the pupils in Class Q was 82 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 |
50
|
50 x 87 =
4350 |
0
|
0
|
4350
|
49
|
49 x 87 =
4263 |
1
|
1 x 82 =
82 |
4345
|
20
|
20 x 87 =
1740 |
30
|
30 x 82 =
2460 |
4200
|
Total scores of Class Q and Class P
= 50 x 84
= 4200
If all the pupils are in Class P,
total scores
= 50 x 87
= 4350
Big difference
= 4350 - 4200
= 150
Small difference
= 87 - 82
= 5
Number of pupils in Class Q
= 150 ÷ 5
= 30
Number of pupils in Class P
= 50 - 30
= 20
Answer(s): 20
