The average test score of a class was 66 marks. After four pupils who scored an average marks of 91 marks transferred out of the class, the average score of the remaining pupils became 62 marks. How many pupils were there in the class in the end?
| |
(1) |
(2) |
| Number |
1 u |
1 u - 4 |
| Value |
66 |
62 |
| Total value |
66 u |
62 u - 248 |
Number of pupils at first = 1 u
Total score at first
= 1 u x 66
= 66 u
Total score of the 4 pupils
= 4 x 91
= 364
Total marks scored after 4 pupils transferred out
= 62 x (1 u - 4)
= 62 u - 248
66 u - 364 = 62 u - 248
66 u - 62 u = 364 - 248
4 u = 116
1 u = 116 ÷ 4 = 29
Number of pupils in the class in the end
= 1 u - 4
= 29 - 4
= 25
Answer(s): 25
