65 students from Class B and Class C took a Mathematics test. The average marks of the students was 84 marks. The average marks of the students in Class B was 86 marks and the average marks of the students in Class C was 81 marks. How many students were there in Class B?
Students in
Class B |
Total scores in
Class B |
Students in
Class C |
Total scores in
Class C |
Total scores of
Class B and Class C |
65
|
65 x 86 =
5590 |
0
|
0
|
5590
|
64
|
64 x 86 =
5504 |
1
|
1 x 81 =
81 |
5585
|
39
|
39 x 86 =
3354 |
26
|
26 x 81 =
2106 |
5460
|
Total scores of Class C and Class B
= 65 x 84
= 5460
If all the students are in Class B,
total scores
= 65 x 86
= 5590
Big difference
= 5590 - 5460
= 130
Small difference
= 86 - 81
= 5
Number of students in Class C
= 130 ÷ 5
= 26
Number of students in Class B
= 65 - 26
= 39
Answer(s): 39
