The average cost of 7 books is $90.
After 2 new books are added,
the average cost of all the books is $80.
- 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 7 books
= 7 x 90
= $630
Number of books
= 7 + 2
= 9
Total cost of all the books
= 9 x 80
= $720
Total cost of the 2 books that are added
= 720 - 630
= $90
(b)
Average cost of the 2 books that are added
= 90 ÷ 2
= $45
Answer(s): (a) $90; (b) $45