Question 1154837
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The second runner starts a half hour after the first.  Since the first runner runs at 6mph, he has run 3 miles when the second runner starts.<br>
The second runner runs 1mph faster than the first.  The amount of time he needs to make up the 3 miles, at the rate of 1mph, is 3 hours.<br>
ANSWER: 3 hours<br>
Algebraically....:<br>
x = hours the second runner runs
x+0.5 = hours the first runner runs<br>
7x = distance second runner runs
6(x+0.5) = distance first runner runs.<br>
{{{7x = 6(x+0.5)}}}
{{{7x = 6x+3}}}
{{{x = 3}}}<br>