The average cost of 4 books is $90.
After 4 new books are added,
the average cost of all the books is $60.
- 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 90
= $360
Number of books
= 4 + 4
= 8
Total cost of all the books
= 8 x 60
= $480
Total cost of the 4 books that are added
= 480 - 360
= $120
(b)
Average cost of the 4 books that are added
= 120 ÷ 4
= $30
Answer(s): (a) $120; (b) $30