The average cost of 8 books is $90.
After 4 new books are added,
the average cost of all the books is $80.
- 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 90
= $720
Number of books
= 8 + 4
= 12
Total cost of all the books
= 12 x 80
= $960
Total cost of the 4 books that are added
= 960 - 720
= $240
(b)
Average cost of the 4 books that are added
= 240 ÷ 4
= $60
Answer(s): (a) $240; (b) $60