Billy is selling 800 story books. He sold 75% of them at $12 each, 60% of the remainder at a discount of 25% and the rest at cost price. He made a profit of $2179. Find the cost price of a story book.
Price |
$12 |
$9 |
Cost Price |
Percent |
75% |
25% |
|
|
15% |
10% |
Number |
600 |
120 |
Not needed |
Amount collected |
$7200 |
$1080 |
Not needed |
Number of story books sold at $12
= 75% x 800
=
75100 x 800
= 600
Price after 25% discount
= 75% x 12
=
75100 x 12
= $9
Remaining story books
= 800 - 600
= 200
Number of story books sold at $9
= 60% x 200
=
60100 x 200
= 120
Number of story books sold at $12 or 25% discount
= 600 + 120
= 720
Total amount collected from the sale of 600 story books
= 600 x 12
= $7200
Total amount collected from the sale of the other 120 story books
= 120 x 9
= $1080
Total amount collected from the sale of story books sold at $12 or 25% discount
= 7200 + 1080
= $8280
Cost price of 720 story books
= 8280 - 2179
= $7200
Cost price of 1 story book
= 7200 ÷ 720
= $10
Answer(s): $10