The average test score of a class was 61 marks. After four pupils who scored an average marks of 96 marks transferred out of the class, the average score of the remaining pupils became 51 marks. How many pupils were there in the class at first?
|
(1) |
(2) |
Number |
1 u |
1 u - 4 |
Value |
61 |
51 |
Total value |
61 u |
51 u - 204 |
Number of pupils at first = 1 u
Total score at first
= 1 u x 61
= 61 u
Total score of the 4 pupils
= 4 x 96
= 384
Total marks scored after 4 pupils transferred out
= 51 x (1 u - 4)
= 51 u - 204
61 u - 384 = 51 u - 204
61 u - 51 u = 384 - 204
10 u = 180
1 u = 180 ÷ 10 = 18
Number of pupils in the class at first
= 1 u
= 18
Answer(s): 18