# Twelve books cost me $48. What would 13 books cost me?

##### 1 Answer

#### Answer:

#### Explanation:

The problem tells you that **books** cost **book** cost.

To do that, use the given ratio as a *conversion factor* to go from number of books to cost. You will end up with

#1 color(red)(cancel(color(black)("book"))) * overbrace( ($48)/(12color(red)(cancel(color(black)("books")))))^(color(blue)("given by the problem")) = $4#

You now converted the *equivalent* **books**

#13 color(red)(cancel(color(black)("books"))) * ($4)/(1color(red)(cancel(color(black)("book")))) = color(darkgreen)(ul(color(black)($52)))#

Notice that you don't have to use the simplified ratio here, you can work directly with the one given to you by the problem

#13 color(red)(cancel(color(black)("books"))) * ($48)/(12color(red)(cancel(color(black)("books")))) = 13/12 * $48 = color(darkgreen)(ul(color(black)($52)))#