The average test score of a class was 59 marks. After three pupils who scored an average marks of 90 marks transferred out of the class, the average score of the remaining pupils became 56 marks. How many pupils were there in the class in the end?
|
(1) |
(2) |
Number |
1 u |
1 u - 3 |
Value |
59 |
56 |
Total value |
59 u |
56 u - 168 |
Number of pupils at first = 1 u
Total score at first
= 1 u x 59
= 59 u
Total score of the 3 pupils
= 3 x 90
= 270
Total marks scored after 3 pupils transferred out
= 56 x (1 u - 3)
= 56 u - 168
59 u - 270 = 56 u - 168
59 u - 56 u = 270 - 168
3 u = 102
1 u = 102 ÷ 3 = 34
Number of pupils in the class in the end
= 1 u - 3
= 34 - 3
= 31
Answer(s): 31