The average test score of a class was 55 marks. After two pupils who scored an average marks of 91 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 - 2 |
| Value |
55 |
53 |
| Total value |
55 u |
53 u - 106 |
Number of pupils at first = 1 u
Total score at first
= 1 u x 55
= 55 u
Total score of the 2 pupils
= 2 x 91
= 182
Total marks scored after 2 pupils transferred out
= 53 x (1 u - 2)
= 53 u - 106
55 u - 182 = 53 u - 106
55 u - 53 u = 182 - 106
2 u = 76
1 u = 76 ÷ 2 = 38
Number of pupils in the class at first
= 1 u
= 38
Answer(s): 38
