The average cost of 6 books is $70.
After 4 new books are added,
the average cost of all the books is $50.
- 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 70
= $420
Number of books
= 6 + 4
= 10
Total cost of all the books
= 10 x 50
= $500
Total cost of the 4 books that are added
= 500 - 420
= $80
(b)
Average cost of the 4 books that are added
= 80 ÷ 4
= $20
Answer(s): (a) $80; (b) $20