The average cost of 6 books is $70.
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 6 books
= 6 x 70
= $420
Number of books
= 6 + 3
= 9
Total cost of all the books
= 9 x 50
= $450
Total cost of the 3 books that are added
= 450 - 420
= $30
(b)
Average cost of the 3 books that are added
= 30 ÷ 3
= $10
Answer(s): (a) $30; (b) $10