The average cost of some books is $40.
If 8 of the books are now each $14 more and
2 of the books are now each $8 less,
the average cost of the books becomes $46.
How many books are there altogether?
|
Case 1 |
Case 2 |
Number |
1 u |
1 u |
Value |
40 |
46 |
Total value |
40 u |
46 u |
Number of books at first = 1 u
Number of books in the end = 1 u
Total cost of the books at first
= 40 x 1 u
= 40 u
Increase in the cost after 8 books are now each $14 more and 2 books are now each $8 less
= 8 x 14 - 2 x 8
= 112 - 16
= $96
Total cost of books after 8 books are now each $14 more and 2 books are now each $8 less
= 40 u + 96
Total cost of books in the end
= 46 x 1 u
= 46 u
46 u = 40 u + 96
46 u - 40 u = 96
6 u = 96
1 u = 96 ÷ 6 = 16
Number of books in the end
= 1 u
= 16
Answer(s): 16