Question

4a. In a book store, for every 9 books sold, 13 magazines were sold. If they had a 572 sales, how many of the sales were for books?

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Answer 1

234 books.

Explanation:

You need to set up a proportion. Be careful to note what it looks like and the explanation that follows.

9 books 13 magazines

======= = ===========

x 572 - x Cross multiply

What you want is the number of book sales from the proportion.

However all you have is the ratio of books to magazines. So you have to set up the total sales to magazines, which is a bit awkward. 572 - x is the number of magazine sales.

9*(572 - x) = 13x Remove the brackets on the left.

5148- 9x = 13x Add 9x to both sides.

5148 = 13x + 9x Transpose and add the right.

22x = 5148 Divide by 22

x = 5148/22

x = 234

234 books were sold.