The average test score of a class was 68 marks. After three pupils who scored an average marks of 98 marks transferred out of the class, the average score of the remaining pupils became 53 marks. How many pupils were there in the class at first?
| |
(1) |
(2) |
| Number |
1 u |
1 u - 3 |
| Value |
68 |
53 |
| Total value |
68 u |
53 u - 159 |
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 98
= 294
Total marks scored after 3 pupils transferred out
= 53 x (1 u - 3)
= 53 u - 159
68 u - 294 = 53 u - 159
68 u - 53 u = 294 - 159
15 u = 135
1 u = 135 ÷ 15 = 9
Number of pupils in the class at first
= 1 u
= 9
Answer(s): 9
