document.write( "Question 596396: An express train travels 150 miles in the same time a freight train goes 100 miles. Find their average speeds if the freight train travels 20 mph less than the express train \n" ); document.write( "

Algebra.Com's Answer #377712 by josmiceli(19441) $\"\"$ $\"About$

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L:et $\"+t+\"$ = the same time for both trains in hours
\n" ); document.write( "Let $\"+s+\"$ = the speed of the express train in mi/hr
\n" ); document.write( " $\"+s+-+20+\"$ = the speed of the freight train in mi/hr
\n" ); document.write( "----------------
\n" ); document.write( "Equation for express train:
\n" ); document.write( "(1) $\"+150+=+s%2At+\"$
\n" ); document.write( "Equation for freight train:
\n" ); document.write( "(2) $\"+100+=+%28+s+-+20+%29%2At+\"$
\n" ); document.write( "----------------
\n" ); document.write( "(2) $\"+100+=+s%2At+-+20t+\"$
\n" ); document.write( "Substitute (1) into (2)
\n" ); document.write( "(2) $\"+100+=+150+-+20t+\"$
\n" ); document.write( "(2) $\"+20t+=+150+-+100+\"$
\n" ); document.write( "(2) $\"+20t+=+50+\"$
\n" ); document.write( "(2) $\"+t+=+2.5+\"$ hrs
\n" ); document.write( "----------------
\n" ); document.write( "(1) $\"+150+=+s%2At+\"$
\n" ); document.write( "(1) $\"+150+=+s%2A2.5+\"$
\n" ); document.write( "(1) $\"+s+=+150%2F2.5+\"$
\n" ); document.write( "(1) $\"+s+=+60+\"$ mi/hr
\n" ); document.write( "and
\n" ); document.write( "(2) $\"+100+=+%28+s+-+20+%29%2At+\"$
\n" ); document.write( "(2) $\"+100+=+%28+s+-+20+%29%2A2.5+\"$
\n" ); document.write( "(2) $\"+100+%2F+2.5+=+s+-+20+\"$
\n" ); document.write( "(2) $\"+s+-+20+=+40+\"$
\n" ); document.write( "-----------------
\n" ); document.write( "The average speed of the express train in 60 mi/hr
\n" ); document.write( "The average speed of the freight train in 40 mi/hr \n" ); document.write( "

\n" );