If 12 gallons of gas cost $32.64, what is the rate of change of this linear function? Write a direct variation equation for this situation.

Answer 1

Let y = cost and x = gallons:

y = kx

32.64 = k·12

2.72 = k

k is the rate of change in units of dollars per gallon. The final direct variation equation is:

y = 2.72x