The average cost of some books is $52.
When another 6 books are added,
the total cost increases by $260.
The average cost becomes $50.
How many books are there in the end?
|
Case 1 |
Case 2 |
Number |
1 u |
1 u + 6 |
Value |
52 |
50 |
Total value |
52 u |
50 u + 300 |
Number of books at first = 1 u
Number of books in the end = 1 u + 6
Total cost of books at first
= 1 u x 52
= 52 u
Total cost of the books in the end
= 50 x (1 u + 6)
= 50 u + 300
52 u + 260 = 50 u + 300
52 u - 50 u = 300 - 260
2 u = 40
1 u = 40 ÷ 2 = 20
Number of books in the end
= 1 u + 6
= 20 + 6
= 26
Answer(s): 26