51 pupils from Class N and Class P took a Mathematics test. The average marks of the pupils was 83 marks. The average marks of the pupils in Class N was 87 marks and the average marks of the pupils in Class P was 81 marks. How many pupils were there in Class N?
Pupils in
Class N |
Total scores in
Class N |
Pupils in
Class P |
Total scores in
Class P |
Total scores of
Class N and Class P |
51
|
51 x 87 =
4437 |
0
|
0
|
4437
|
50
|
50 x 87 =
4350 |
1
|
1 x 81 =
81 |
4431
|
17
|
17 x 87 =
1479 |
34
|
34 x 81 =
2754 |
4233
|
Total scores of Class P and Class N
= 51 x 83
= 4233
If all the pupils are in Class N,
total scores
= 51 x 87
= 4437
Big difference
= 4437 - 4233
= 204
Small difference
= 87 - 81
= 6
Number of pupils in Class P
= 204 ÷ 6
= 34
Number of pupils in Class N
= 51 - 34
= 17
Answer(s): 17
