The average test score of a class was 60 marks. After three students who scored an average marks of 90 marks transferred out of the class, the average score of the remaining students became 50 marks. How many students were there in the class in the end?
| |
(1) |
(2) |
| Number |
1 u |
1 u - 3 |
| Value |
60 |
50 |
| Total value |
60 u |
50 u - 150 |
Number of students at first = 1 u
Total score at first
= 1 u x 60
= 60 u
Total score of the 3 students
= 3 x 90
= 270
Total marks scored after 3 students transferred out
= 50 x (1 u - 3)
= 50 u - 150
60 u - 270 = 50 u - 150
60 u - 50 u = 270 - 150
10 u = 120
1 u = 120 ÷ 10 = 12
Number of students in the class in the end
= 1 u - 3
= 12 - 3
= 9
Answer(s): 9
