Question

The amount of money it takes to fill up a gas tank varies directly with the number of gallons bought. It cost $21.87 to fill up a car with gasoline with 9 gallons of gasoline. What is the constant of variation?

Answer 1

i think the answer is

2.43

Answer 2

$2.43 per gallon of gas.

Explanation:

We have been given that the amount of money it takes to fill up a gas tank varies directly with the number of gallons bought.

We know that the equation for two directly proportional quantities is in form:
`y=kx`, where,

k = The constant of variation and y is directly proportional to x.

To find the constant of variation for our given equation, we will substitute the given values in above equation as:

`\$21.87=k*9\text{ gallons}`

Let us divide both sides of our equation by 9 gallons.

`\frac{\$21.87}{9\text{ gallons}}=\frac{k*9\text{ gallons}}{9\text{ gallons}}`

`\frac{\$2.43}{\text{ gallon}}=k`

Therefore, the constant of variation is $2.43 per gallon of gas.