Bill has to buy 9 pounds of bananas. Bananas are on sale at 5 pounds for $1. Bill begins to find the cost of 9 bananas with a proportion.

5 pounds of bananas / $1   =   how much money / 9 pounds of bananas

5 / 1 = X / 9

• Should Bill continue solving the problem the way he has it set up or does he need to set it up differently?

In order to see if Bill is solving the proportion correctly to find the cost of 9 pounds of bananas, you need to make sure you understand the problem and know how to set up a proportion. Bill needs to find the cost of 9 pounds of bananas knowing that 5 pounds cost $1.

When setting up a proportion, you need to remember that your ratios need to be set up with the same units on the top for both ratios as well as on the bottom. For example, in this case, no matter the pounds or dollars, the ratios need to be set up with only either pounds or dollars on the top and the other on the bottom. So it should be set up either pounds / dollars = pounds / dollars or dollars / pounds = dollars / pounds.

Knowing how to set up a proportion, you begin to set up the proportion one of two ways.

$1 / 5 lbs = $X / 9 lbs
or
5 lbs / $1 = 9 lbs / $X

Notice how whatever units are on the top of one ratio it must be the same on the other ratio. The same thing with the bottom of the ratio.

As you look over the choices given to you, you need to find the ratios and proportion where either pounds of bananas are on the top in both or dollars are on the top in both. In this case you find that letter C has dollars / pounds = dollars / pounds. The correct answer to this problem is letter C.