Question

David is driving on the highway. He begins the trip with 14 gallons of gas in his car. The car uses up one gallon of gas every 20 miles. Let G represent the number of gallons of gas he has left in his tank, and let D represent the total distance (in miles) he has traveled. Write an equation relating G to D, and then graph your equation.

Answer 1

Answer:

$G = -D/20 + 14$

Graph in the image attached.

Step-by-step explanation:

Using the model of a linear equation, we have:

$G = aD + b$

'b' is the y-intercept of the equation, that is, the inicial value of G, when D = 0.

So if David starts the trip with 14 gallons of gas, we have b = 14.

'a' is the slope of the line, that is, an increase of 1 in the value of D causes an increase of 'a' in the value of G.

So if the car uses one gallon every 20 miles, the value of a is -1/20 (an increase of 20 in D causes a decrease of 1 in G).]

So our equation is:

$G = -D/20 + 14$

The graph of this equation is in the image attached.