The average cost of 9 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 9 books
= 9 x 90
= $810
Number of books
= 9 + 2
= 11
Total cost of all the books
= 11 x 80
= $880
Total cost of the 2 books that are added
= 880 - 810
= $70
(b)
Average cost of the 2 books that are added
= 70 ÷ 2
= $35
Answer(s): (a) $70; (b) $35