The average test score of a class was 69 marks. After three students who scored an average marks of 97 marks transferred out of the class, the average score of the remaining students became 57 marks. How many students were there in the class in the end?
| |
(1) |
(2) |
| Number |
1 u |
1 u - 3 |
| Value |
69 |
57 |
| Total value |
69 u |
57 u - 171 |
Number of students at first = 1 u
Total score at first
= 1 u x 69
= 69 u
Total score of the 3 students
= 3 x 97
= 291
Total marks scored after 3 students transferred out
= 57 x (1 u - 3)
= 57 u - 171
69 u - 291 = 57 u - 171
69 u - 57 u = 291 - 171
12 u = 120
1 u = 120 ÷ 12 = 10
Number of students in the class in the end
= 1 u - 3
= 10 - 3
= 7
Answer(s): 7
