The average cost of 6 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 6 books
= 6 x 90
= $540
Number of books
= 6 + 4
= 10
Total cost of all the books
= 10 x 80
= $800
Total cost of the 4 books that are added
= 800 - 540
= $260
(b)
Average cost of the 4 books that are added
= 260 ÷ 4
= $65
Answer(s): (a) $260; (b) $65