The average cost of 4 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 4 books
= 4 x 40
= $160
Number of books
= 4 + 4
= 8
Total cost of all the books
= 8 x 30
= $240
Total cost of the 4 books that are added
= 240 - 160
= $80
(b)
Average cost of the 4 books that are added
= 80 ÷ 4
= $20
Answer(s): (a) $80; (b) $20