The average cost of 4 books is $80.
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 4 books
= 4 x 80
= $320
Number of books
= 4 + 3
= 7
Total cost of all the books
= 7 x 50
= $350
Total cost of the 3 books that are added
= 350 - 320
= $30
(b)
Average cost of the 3 books that are added
= 30 ÷ 3
= $10
Answer(s): (a) $30; (b) $10