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
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:
(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.).