The average cost of some books is $49.
If 3 of the books are now each $14 more,
the average cost of the books becomes $52.
How many books are there altogether?
|
Case 1 |
Case 2 |
Number |
1 u |
1 u |
Value |
49 |
52 |
Total value |
49 u |
52 u |
Number of books at first = 1 u
Number of books in the end = 1 u
Total cost of the books at first
= 49 x 1 u
= 49 u
Total cost of books in the end
= 52 x 1 u
= 52 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
= 49 u + 42
52 u = 49 u + 42
52 u - 49 u = 42
3 u = 42
1 u = 42 ÷ 3 = 14
Number of books in the end
= 1 u
= 14
Answer(s): 14