55 pupils from Class H and Class J took a Mathematics test. The average marks of the pupils was 85 marks. The average marks of the pupils in Class H was 89 marks and the average marks of the pupils in Class J was 78 marks. How many pupils were there in Class H?
Pupils in
Class H |
Total scores in
Class H |
Pupils in
Class J |
Total scores in
Class J |
Total scores of
Class H and Class J |
55
|
55 x 89 =
4895 |
0
|
0
|
4895
|
54
|
54 x 89 =
4806 |
1
|
1 x 78 =
78 |
4884
|
35
|
35 x 89 =
3115 |
20
|
20 x 78 =
1560 |
4675
|
Total scores of Class J and Class H
= 55 x 85
= 4675
If all the pupils are in Class H,
total scores
= 55 x 89
= 4895
Big difference
= 4895 - 4675
= 220
Small difference
= 89 - 78
= 11
Number of pupils in Class J
= 220 ÷ 11
= 20
Number of pupils in Class H
= 55 - 20
= 35
Answer(s): 35
