52 students from Class Y and Class Z took a Mathematics test. The average marks of the students was 81 marks. The average marks of the students in Class Y was 84 marks and the average marks of the students in Class Z was 80 marks. How many students were there in Class Y?
Students in
Class Y |
Total scores in
Class Y |
Students in
Class Z |
Total scores in
Class Z |
Total scores of
Class Y and Class Z |
52
|
52 x 84 =
4368 |
0
|
0
|
4368
|
51
|
51 x 84 =
4284 |
1
|
1 x 80 =
80 |
4364
|
13
|
13 x 84 =
1092 |
39
|
39 x 80 =
3120 |
4212
|
Total scores of Class Z and Class Y
= 52 x 81
= 4212
If all the students are in Class Y,
total scores
= 52 x 84
= 4368
Big difference
= 4368 - 4212
= 156
Small difference
= 84 - 80
= 4
Number of students in Class Z
= 156 ÷ 4
= 39
Number of students in Class Y
= 52 - 39
= 13
Answer(s): 13
