Question 702572
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5 miles per hour is 1/12 mile per minute, so one minute after the speeder passes the cop he is 1/12 of a mile ahead.  10 miles per hour is 2/12 of a mile per minute so he catches up in 30 seconds.


If v is the new cop speed, then the speed differential is v - 60, and the speed differential in miles per minute is (v - 60)/60.  Divide the 1/12 mile distance difference by the speed difference.  For this situation it comes out to 5/(v - 60).


Note that this works for the original situation:  5/(70 - 60) = 5/10 = 1/2 minute = 30 seconds. 


John
*[tex \LARGE e^{i\pi}\ +\ 1\ =\ 0]
<font face="Math1" size="+2">Egw to Beta kai to Sigma</font>
My calculator said it, I believe it, that settles it
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