The average cost of 6 books is $30.
After 4 new books are added,
the average cost of all the books is $20.
- What is the total cost of the 4 books that are added?
- What is the average cost of the 4 books that are added?
(a)
Total cost of 6 books
= 6 x 30
= $180
Number of books
= 6 + 4
= 10
Total cost of all the books
= 10 x 20
= $200
Total cost of the 4 books that are added
= 200 - 180
= $20
(b)
Average cost of the 4 books that are added
= 20 ÷ 4
= $5
Answer(s): (a) $20; (b) $5