The average cost of 8 books is $70.
After 4 new books are added,
the average cost of all the books is $50.
- 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 70
= $560
Number of books
= 8 + 4
= 12
Total cost of all the books
= 12 x 50
= $600
Total cost of the 4 books that are added
= 600 - 560
= $40
(b)
Average cost of the 4 books that are added
= 40 ÷ 4
= $10
Answer(s): (a) $40; (b) $10