55 pupils from Class D and Class E took a Mathematics test. The average marks of the pupils was 83 marks. The average marks of the pupils in Class D was 89 marks and the average marks of the pupils in Class E was 74 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 |
55
|
55 x 89 = 4895 |
0
|
0
|
4895
|
54
|
54 x 89 = 4806 |
1
|
1 x 74 = 74 |
4880
|
33
|
33 x 89 = 2937 |
22
|
22 x 74 = 1628 |
4565
|
Total scores of Class E and Class D
= 55 x 83
= 4565
If all the pupils are in Class D,
total scores
= 55 x 89
= 4895
Big difference
= 4895 - 4565
= 330
Small difference
= 89 - 74
= 15
Number of pupils in Class E
= 330 ÷ 15
= 22
Number of pupils in Class D
= 55 - 22
= 33
Answer(s): 33