document.write( "Question 1084090: On a 100km track a train travells the first 30km at a uniform speed of 30km/h . How fast must the train travel the next 70 km so as to average 40km/h for the entire trip? \n" ); document.write( "

Algebra.Com's Answer #698135 by Fombitz(32388) $\"\"$ $\"About$

You can put this solution on YOUR website!
Rate x Time = Distance,
\n" ); document.write( "For the first 30 km,
\n" ); document.write( " $\"30%2At=30\"$
\n" ); document.write( " $\"t=1\"$ $\"hr\"$
\n" ); document.write( "So then to get the average velocity,
\n" ); document.write( "Using the distance formula,
\n" ); document.write( "1. $\"30%2BV%5B2%5D%2At%5B2%5D=100\"$
\n" ); document.write( "and using the average velocity,
\n" ); document.write( "2. $\"%2830%2A1%2BV%5B2%5D%2At%5B2%5D%29%2F%281%2Bt%5B2%5D%29=40\"$
\n" ); document.write( "So then,
\n" ); document.write( " $\"30%2BV%5B2%5D%2At%5B2%5D=40%281%2Bt%5B2%5D%29\"$
\n" ); document.write( "Substituting into 1,
\n" ); document.write( " $\"40%281%2Bt%5B2%5D%29=100\"$
\n" ); document.write( " $\"1%2Bt%5B2%5D=5%2F2\"$
\n" ); document.write( " $\"t%5B2%5D=3%2F2\"$ $\"hr\"$
\n" ); document.write( "So then from 1,
\n" ); document.write( " $\"30%2BV%5B2%5D%283%2F2%29=100\"$
\n" ); document.write( " $\"V%5B2%5D%283%2F2%29=70\"$
\n" ); document.write( " $\"V%5B2%5D=140%2F3\"$ $\"km%2Fhr\"$ \r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "

\n" );