The average cost of 5 books is $50.
After 4 new books are added,
the average cost of all the books is $30.
- 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 5 books
= 5 x 50
= $250
Number of books
= 5 + 4
= 9
Total cost of all the books
= 9 x 30
= $270
Total cost of the 4 books that are added
= 270 - 250
= $20
(b)
Average cost of the 4 books that are added
= 20 ÷ 4
= $5
Answer(s): (a) $20; (b) $5