document.write( "Question 409917: 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 \n" ); document.write( "

Algebra.Com's Answer #288419 by ankor@dixie-net.com(22740) $\"\"$ $\"About$

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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
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\n" ); document.write( "I don't think it is possible to go fast enough to average 40 km/hr
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\n" ); document.write( "Let s = speed required to average a round trip speed of 40 km/hr
\n" ); document.write( "Let d = one-way distance
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\n" ); document.write( " $\"d%2F20\"$ + $\"d%2Fs\"$ = $\"%282d%29%2F40\"$
\n" ); document.write( "multiply equation by 40s
\n" ); document.write( "2sd + 40d = 2sd
\n" ); document.write( "divide thru by d
\n" ); document.write( "2s + 40 = 2s
\n" ); document.write( "You can see this is not a valid equation, so not possible
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