60 students from Class W and Class X took a Mathematics test. The average marks of the students was 85 marks. The average marks of the students in Class W was 91 marks and the average marks of the students in Class X was 82 marks. How many students were there in Class W?
Students in
Class W |
Total scores in
Class W |
Students in
Class X |
Total scores in
Class X |
Total scores of
Class W and Class X |
60
|
60 x 91 =
5460 |
0
|
0
|
5460
|
59
|
59 x 91 =
5369 |
1
|
1 x 82 =
82 |
5451
|
20
|
20 x 91 =
1820 |
40
|
40 x 82 =
3280 |
5100
|
Total scores of Class X and Class W
= 60 x 85
= 5100
If all the students are in Class W,
total scores
= 60 x 91
= 5460
Big difference
= 5460 - 5100
= 360
Small difference
= 91 - 82
= 9
Number of students in Class X
= 360 ÷ 9
= 40
Number of students in Class W
= 60 - 40
= 20
Answer(s): 20
