The average cost of 6 books is $40.
After 3 new books are added,
the average cost of all the books is $30.
- 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 6 books
= 6 x 40
= $240
Number of books
= 6 + 3
= 9
Total cost of all the books
= 9 x 30
= $270
Total cost of the 3 books that are added
= 270 - 240
= $30
(b)
Average cost of the 3 books that are added
= 30 ÷ 3
= $10
Answer(s): (a) $30; (b) $10