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?

Answer 1

Based on a proportion comparing the cost of 15 gallons of gas ($45) to 5 gallons, we can determine that 5 gallons will cost $15 after setting up and solving the proportion (15 gallons / $45) = (5 gallons / x dollars).

Step-by-step explanation:

To determine how much 5 gallons of gas will cost based on the given information, we set up a proportion using fractional notation. The original purchase is 15 gallons for $45, which gives us a ratio. The cost for 5 gallons is what we need to find. To set up the proportion, we use the ratio (15 gallons / $45) and the unknown ratio (5 gallons / x dollars), where x represents the cost for 5 gallons.

The proportion is set up as follows:

(15 gallons / $45) = (5 gallons / x dollars)
Now, we cross-multiply to solve for x:

15 * x = 45 * 5

15x = 225

x = 225 / 15

x = $15

Therefore, based on the proportion, 5 gallons of gas will cost $15.

Keeping a record of fuel purchases can be beneficial for personal transportation cost management, especially considering that a typical American may buy about 400 gallons a year. It's also useful to know the car's approximate fuel economy and to calculate costs when sharing a ride, which is the total gallons used divided by the number of people.