72 students from Class K and Class L took a Mathematics test. The average marks of the students was 80 marks. The average marks of the students in Class K was 85 marks and the average marks of the students in Class L was 73 marks. How many students were there in Class K?
Students in
Class K |
Total scores in
Class K |
Students in
Class L |
Total scores in
Class L |
Total scores of
Class K and Class L |
72
|
72 x 85 =
6120 |
0
|
0
|
6120
|
71
|
71 x 85 =
6035 |
1
|
1 x 73 =
73 |
6108
|
42
|
42 x 85 =
3570 |
30
|
30 x 73 =
2190 |
5760
|
Total scores of Class L and Class K
= 72 x 80
= 5760
If all the students are in Class K,
total scores
= 72 x 85
= 6120
Big difference
= 6120 - 5760
= 360
Small difference
= 85 - 73
= 12
Number of students in Class L
= 360 ÷ 12
= 30
Number of students in Class K
= 72 - 30
= 42
Answer(s): 42
