You fill your car with 15 gallons of gas at a cost of $45. Using fractional notation, how do you write a proportion that shows how much 5 gallons of gas will cost? Use x

Question

x
to represent the unknown cost.

Answer 1

To express the relationship of the cost of gas in a proportion, you can set it up as follows:

You know that 15 gallons of gas costs $45. We can write this as a fraction:

\[ \frac{15 \text{ gallons}}{45 \text{ dollars}} \]

Now, we want to find the cost (represented by \( x \)) of 5 gallons of gas. This can also be written as:

\[ \frac{5 \text{ gallons}}{x \text{ dollars}} \]

Now, we can set up the proportion:

\[ \frac{15}{45} = \frac{5}{x} \]

This proportion states that the ratio of gallons to cost remains constant.