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 Math Central Quandaries & Queries
 Question from Laura, a student: The monthly cost of driving a car depends on the number of miles driven. Lynn found that in May it cost her $300 to drive 480 miles and in June it cost her$460 to drive 800 miles. Question: Express the monthly cost C as a function of the distance driven d, assuming that a linear relationship gives a suitable model.

Laura,

How much more did it cost ("rise") in June?

How many more miles ("run") did she drive?

What is the slope (rise/run, "m") of the line?

How many fewer miles than in May would she drive if she did not drive at all?

Using the same ratio, how much less than in May would it cost?

How much ("y intercept", "b") is that?

Good Hunting!
RD

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