<PRE><B>Question 409917</B>
if you drive with a speed of 20km/hr, how fast you must go again returning by the same route for your average speed to be 40km/hr
:
I don&#39;t think it is possible to go fast enough to average 40 km/hr
:
Let s = speed required to average a round trip speed of 40 km/hr
Let d = one-way distance
:
{{{d/20}}} + {{{d/s}}} = {{{(2d)/40}}}
multiply equation by 40s
2sd + 40d = 2sd
divide thru by d
2s + 40 = 2s
You can see this is not a valid equation, so not possible
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