The average cost of some books is $43.
If 5 of the books are now each $12 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 |
43 |
48 |
Total value |
43 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
= 43 x 1 u
= 43 u
Total cost of books in the end
= 48 x 1 u
= 48 u
Increase in the cost when 5 books are now each $12 more
= 5 x 12
= $60
Total cost of books after 5 books are now each $12 more
= 43 u + 60
48 u = 43 u + 60
48 u - 43 u = 60
5 u = 60
1 u = 60 ÷ 5 = 12
Number of books in the end
= 1 u
= 12
Answer(s): 12