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

Answer:

$2.43 per gallon of gas.

Step-by-step 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.