The average cost of 8 books is $80.
After 4 new books are added,
the average cost of all the books is $60.
- 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 8 books
= 8 x 80
= $640
Number of books
= 8 + 4
= 12
Total cost of all the books
= 12 x 60
= $720
Total cost of the 4 books that are added
= 720 - 640
= $80
(b)
Average cost of the 4 books that are added
= 80 ÷ 4
= $20
Answer(s): (a) $80; (b) $20