# Elapsed Time

## From start to stop, from beginning to end

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Practice Elapsed Time

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Running Time

Credit: Chris Desmond/U.S. Navy
Source: http://commons.wikimedia.org/wiki/File:US_Navy_030506-N-5862D-128_An_instructor_in_the_Freedom_Hall_athletic_complex_uses_a_stopwatch_while_recruits_run_a_1.5-mile_track_during_a_Physical_Fitness_Test_(PFT).jpg

Have you ever run a road race or dreamed of one day running a marathon? Runners all over the world run that famous 26.2 miles each and every year. They spend hours and hours training so that they can run their best race on race day. Did you know that while training runners not only run but also calculate times?

#### Why It Matters

Elapsed time is the difference between times. Imagine that you are training for your first marathon. You set out at 8:10 a.m. for a run of 5 miles. You return home at 8:55 a.m.

Credit: Chris Brown
Source: http://www.flickr.com/photos/zoonabar/2432302766/

You can now find the difference between the start time and the end time of your run. This will give you the elapsed time, or the amount of time that it took you to run those five miles.

\begin{align*}8:55 - 8:10 = 45 \ \mathrm{minutes}\end{align*}

Your elapsed time was 45 minutes. If you divide that by the number of miles, you can see that you were averaging a 9-minute mile. Assuming your rate stays the same, you can predict the length of time that it will take you to run 26.2 miles. Elapsed time is a useful tool in preparing for a marathon.

Take a look at this video of the finish of the 2012 Chicago Marathon: http://www.youtube.com/watch?v=r_HMvbboBUI

#### Explore More

Use the links below to explore elapsed time in a fun, interactive way!

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