document.write( "Question 420155: Two trains leave a city on parallel tracks,traveling the same direction. The passenger train is going twice as fast as the freight train. After 45 minutes, the trains are 30 miles apart. Find the speed of each train. \n" ); document.write( "

Algebra.Com's Answer #293656 by josmiceli(19441) $\"\"$ $\"About$

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Write an equation for both trains
\n" ); document.write( "Let $\"s\"$ = speed of freight train
\n" ); document.write( "passenger train
\n" ); document.write( "(1) $\"d%2B+30+=+2s%2A%283%2F4%29\"$
\n" ); document.write( "freight train
\n" ); document.write( "(2) $\"d+=+s%2A%283%2F4%29\"$
\n" ); document.write( "------------------
\n" ); document.write( "Substitute (2) into (1)
\n" ); document.write( "(1) $\"%283%2F4%29%2As++%2B+30+=+%283%2F4%29%2A2s\"$
\n" ); document.write( "(1) $\"3s+%2B+120+=+6s\"$
\n" ); document.write( "(1) $\"3s+=+120\"$
\n" ); document.write( "(1) $\"s+=+40\"$
\n" ); document.write( "and
\n" ); document.write( " $\"2s+=+80\"$
\n" ); document.write( "the speed of the passenger train is 80 mi/hr
\n" ); document.write( "the speed of the freight train is 40 mi/hr
\n" ); document.write( "check:
\n" ); document.write( "(1) $\"d%2B+30+=+80%2A%283%2F4%29\"$
\n" ); document.write( "(1) $\"d+=+60+-+30\"$
\n" ); document.write( " $\"d+=+30\"$ mi
\n" ); document.write( "and
\n" ); document.write( "(2) $\"d+=+40%2A%283%2F4%29\"$
\n" ); document.write( " $\"d+=+30\"$ mi
\n" ); document.write( "OK \n" ); document.write( "

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