The average cost of some books is $42.
If 2 of the books are now each $14 more,
the average cost of the books becomes $44.
How many books are there altogether?
|
Case 1 |
Case 2 |
Number |
1 u |
1 u |
Value |
42 |
44 |
Total value |
42 u |
44 u |
Number of books at first = 1 u
Number of books in the end = 1 u
Total cost of the books at first
= 42 x 1 u
= 42 u
Total cost of books in the end
= 44 x 1 u
= 44 u
Increase in the cost when 2 books are now each $14 more
= 2 x 14
= $28
Total cost of books after 2 books are now each $14 more
= 42 u + 28
44 u = 42 u + 28
44 u - 42 u = 28
2 u = 28
1 u = 28 ÷ 2 = 14
Number of books in the end
= 1 u
= 14
Answer(s): 14