The average test score of a class was 55 marks. After five pupils who scored an average marks of 98 marks transferred out of the class, the average score of the remaining pupils became 50 marks. How many pupils were there in the class at first?
| |
(1) |
(2) |
| Number |
1 u |
1 u - 5 |
| Value |
55 |
50 |
| Total value |
55 u |
50 u - 250 |
Number of pupils at first = 1 u
Total score at first
= 1 u x 55
= 55 u
Total score of the 5 pupils
= 5 x 98
= 490
Total marks scored after 5 pupils transferred out
= 50 x (1 u - 5)
= 50 u - 250
55 u - 490 = 50 u - 250
55 u - 50 u = 490 - 250
5 u = 240
1 u = 240 ÷ 5 = 48
Number of pupils in the class at first
= 1 u
= 48
Answer(s): 48
