The average test score of a class was 69 marks. After three pupils who scored an average marks of 93 marks transferred out of the class, the average score of the remaining pupils became 60 marks. How many pupils were there in the class in the end?
|
(1) |
(2) |
Number |
1 u |
1 u - 3 |
Value |
69 |
60 |
Total value |
69 u |
60 u - 180 |
Number of pupils at first = 1 u
Total score at first
= 1 u x 69
= 69 u
Total score of the 3 pupils
= 3 x 93
= 279
Total marks scored after 3 pupils transferred out
= 60 x (1 u - 3)
= 60 u - 180
69 u - 279 = 60 u - 180
69 u - 60 u = 279 - 180
9 u = 99
1 u = 99 ÷ 9 = 11
Number of pupils in the class in the end
= 1 u - 3
= 11 - 3
= 8
Answer(s): 8