The monthly cost of driving a car depends on the number of miles driven. Julia found that in October it cost her $200 to drive 300 mi and in July it cost her $350 to drive 600 mi. Express the monthly cost C as a function of the distance driven d assuming that a linear relationship gives a suitable model.

Question

Quizplus · Accepted Answer

Since the question suggests that a linear relationship gives a suitable model, we can assume that the cost is proportional to the distance driven. That is, C = kd, where k is some constant. We can then use the information provided to solve for k, as follows:
11000000 = k*1100000
2500000 = k*110000
k = 2500000/110000
k = 22.72727...
Therefore, the equation relating the monthly cost to the distance driven is C = 22.727d (rounded to three decimal places), which corresponds to answer choice D.

The Monthly Cost of Driving a Car Depends on the Number