The average cost of 9 books is $70.
After 2 new books are added,
the average cost of all the books is $60.
- What is the total cost of the 2 books that are added?
- What is the average cost of the 2 books that are added?
(a)
Total cost of 9 books
= 9 x 70
= $630
Number of books
= 9 + 2
= 11
Total cost of all the books
= 11 x 60
= $660
Total cost of the 2 books that are added
= 660 - 630
= $30
(b)
Average cost of the 2 books that are added
= 30 ÷ 2
= $15
Answer(s): (a) $30; (b) $15