The average test score of a class was 68 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 62 marks. How many pupils were there in the class in the end?
| |
(1) |
(2) |
| Number |
1 u |
1 u - 3 |
| Value |
68 |
62 |
| Total value |
68 u |
62 u - 186 |
Number of pupils at first = 1 u
Total score at first
= 1 u x 68
= 68 u
Total score of the 3 pupils
= 3 x 90
= 270
Total marks scored after 3 pupils transferred out
= 62 x (1 u - 3)
= 62 u - 186
68 u - 270 = 62 u - 186
68 u - 62 u = 270 - 186
6 u = 84
1 u = 84 ÷ 6 = 14
Number of pupils in the class in the end
= 1 u - 3
= 14 - 3
= 11
Answer(s): 11
