The average cost of 8 books is $80.
After 4 new books are added,
the average cost of all the books is $70.
- 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 70
= $840
Total cost of the 4 books that are added
= 840 - 640
= $200
(b)
Average cost of the 4 books that are added
= 200 ÷ 4
= $50
Answer(s): (a) $200; (b) $50