The average cost of some books is $46.
If 3 of the books are now each $14 more,
the average cost of the books becomes $48.
How many books are there altogether?
|
Case 1 |
Case 2 |
Number |
1 u |
1 u |
Value |
46 |
48 |
Total value |
46 u |
48 u |
Number of books at first = 1 u
Number of books in the end = 1 u
Total cost of the books at first
= 46 x 1 u
= 46 u
Total cost of books in the end
= 48 x 1 u
= 48 u
Increase in the cost when 3 books are now each $14 more
= 3 x 14
= $42
Total cost of books after 3 books are now each $14 more
= 46 u + 42
48 u = 46 u + 42
48 u - 46 u = 42
2 u = 42
1 u = 42 ÷ 2 = 21
Number of books in the end
= 1 u
= 21
Answer(s): 21