Hint for Problem 9

Let's say I drive up to Magic Mountain next month to ride some roller coasters. It's roughly 180 miles away up north of LA, for those who don't know. If I drive a nice steady 60 mph, how long would it take me to get there? The relationship between distance, speed, and time is given by

distance = time × speed (1)

or

 d = t s (2)

From Equation 2, you will probably see that you can answer my question easily. Since d = t s, all you have to do is divide the distance (180 miles) by the speed (60 miles/hour), and you get the time, which in my case is 3 hours.

You may have also noticed that Equation 2 looks just like the equation for a straight line:

 y = m x (3)

(compare Equations 2 and 3). That means that if you plot a graph with distance on the Y-axis and speed on the X-axis, you will get a straight line whose slope has the units of time (years, seconds, etc.).

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