56 pupils from Class D and Class E took a Mathematics test. The average marks of the pupils was 80 marks. The average marks of the pupils in Class D was 85 marks and the average marks of the pupils in Class E was 78 marks. How many pupils were there in Class D?
Pupils in Class D |
Total scores in Class D |
Pupils in Class E |
Total scores in Class E |
Total scores of Class D and Class E |
56
|
56 x 85 = 4760 |
0
|
0
|
4760
|
55
|
55 x 85 = 4675 |
1
|
1 x 78 = 78 |
4753
|
16
|
16 x 85 = 1360 |
40
|
40 x 78 = 3120 |
4480
|
Total scores of Class E and Class D
= 56 x 80
= 4480
If all the pupils are in Class D,
total scores
= 56 x 85
= 4760
Big difference
= 4760 - 4480
= 280
Small difference
= 85 - 78
= 7
Number of pupils in Class E
= 280 ÷ 7
= 40
Number of pupils in Class D
= 56 - 40
= 16
Answer(s): 16