The average cost of 5 books is $60.
After 4 new books are added,
the average cost of all the books is $40.
- What is the total cost of the 4 books that are added?
- What is the average cost of the 4 books that are added?
(a)
Total cost of 5 books
= 5 x 60
= $300
Number of books
= 5 + 4
= 9
Total cost of all the books
= 9 x 40
= $360
Total cost of the 4 books that are added
= 360 - 300
= $60
(b)
Average cost of the 4 books that are added
= 60 ÷ 4
= $15
Answer(s): (a) $60; (b) $15