**QUESTION:** In one week, a bookstore sold 1,260 books. The pie chart shows information about the 3 different types of books sold. The angle for the paperback portion is 224\degree. The ratio of hardbacks to audiobooks is 3:1. Work out the number of audiobooks sold by this bookstore in one week.

**ANSWER:** We know that the formula for finding the angle is

\text{angle }=\dfrac{\text{number in one category}}{\text{sum of all categories}}\times 360

This time we know the angle (224), and the sum of all categories (1,260). So, the equation becomes

224\degree =\dfrac{\text{paperbacks sold}}{1,260}\times360

Divide by 360 and then multiply by 1,260 to get

\text{paperbacks sold}=\dfrac{224}{360}\times1,260=784

The number of paperbacks sold is 784, so the number of other books sold is 1,260-784=476. The ratio of hardbacks:audiobooks is 3:1, so audiobooks constitute 1 part out of 4 in the ratio. Therefore, we get

\text{audiobooks sold }=\dfrac{476}{4}=119