The average cost of 5 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 5 books
= 5 x 70
= $350
Number of books
= 5 + 4
= 9
Total cost of all the books
= 9 x 50
= $450
Total cost of the 4 books that are added
= 450 - 350
= $100
(b)
Average cost of the 4 books that are added
= 100 ÷ 4
= $25
Answer(s): (a) $100; (b) $25