The average cost of 9 books is $60.
After 3 new books are added,
the average cost of all the books is $50.
- What is the total cost of the 3 books that are added?
- What is the average cost of the 3 books that are added?
(a)
Total cost of 9 books
= 9 x 60
= $540
Number of books
= 9 + 3
= 12
Total cost of all the books
= 12 x 50
= $600
Total cost of the 3 books that are added
= 600 - 540
= $60
(b)
Average cost of the 3 books that are added
= 60 ÷ 3
= $20
Answer(s): (a) $60; (b) $20