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 to represent the unknown cost.

Question

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 to represent the unknown cost.

Answer 1

The proportion can be set up as:

15 gallons / $45 = 5 gallons / x

This can be written in fractional notation as:

(15/45) = (5/x)

Which simplifies to:

1/3 = 5/x

Now, cross multiply to solve for x:

1 * x = 3 * 5
x = 15

Therefore, 5 gallons of gas will cost $15.