Question 1169385
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The dogs will run toward each other for  {{{500/(10+10)}}} = {{{500/20}}} = {{{50/2}}} = 25 seconds.


During this time, the traveling distance for a flea is its rate times 25, i.e. 25*25 = 625 ft.   <U>ANSWER</U>.
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Solved.


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It is very old and very well known entertainment Travel & Distance problem.