65 students from Class D and Class E took a Mathematics test. The average marks of the students was 81 marks. The average marks of the students in Class D was 87 marks and the average marks of the students in Class E was 74 marks. How many students were there in Class D?
Students in
Class D |
Total scores in
Class D |
Students in
Class E |
Total scores in
Class E |
Total scores of
Class D and Class E |
65
|
65 x 87 =
5655 |
0
|
0
|
5655
|
64
|
64 x 87 =
5568 |
1
|
1 x 74 =
74 |
5642
|
35
|
35 x 87 =
3045 |
30
|
30 x 74 =
2220 |
5265
|
Total scores of Class E and Class D
= 65 x 81
= 5265
If all the students are in Class D,
total scores
= 65 x 87
= 5655
Big difference
= 5655 - 5265
= 390
Small difference
= 87 - 74
= 13
Number of students in Class E
= 390 ÷ 13
= 30
Number of students in Class D
= 65 - 30
= 35
Answer(s): 35
