The average cost of 8 books is $40.
After 4 new books are added,
the average cost of all the books is $30.
- 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 40
= $320
Number of books
= 8 + 4
= 12
Total cost of all the books
= 12 x 30
= $360
Total cost of the 4 books that are added
= 360 - 320
= $40
(b)
Average cost of the 4 books that are added
= 40 ÷ 4
= $10
Answer(s): (a) $40; (b) $10