document.write( "Question 549899: A train leaves the station at 6:00 PM traveling west at 80 mi/h. On a parallel track, a second train leaves the station 3 hours later traveling west at 100 mi/h. At what time will the second train catch up with the first? \n" ); document.write( "

Algebra.Com's Answer #358167 by josmiceli(19441) $\"\"$ $\"About$

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The 1st train has a head start of
\n" ); document.write( " $\"+80%2A3+=+240+\"$ mi
\n" ); document.write( "Start a stopwatch when the 2nd train leaves
\n" ); document.write( "Let $\"d\"$ = distance 2nd train goes until they meet
\n" ); document.write( "Let $\"t\"$ = time on stopwatch when they meet
\n" ); document.write( "---------------
\n" ); document.write( "2nd train:
\n" ); document.write( " $\"+d+=+100t+\"$
\n" ); document.write( "1st train:
\n" ); document.write( " $\"+d+-+240+=+80t+\"$
\n" ); document.write( "-----------------
\n" ); document.write( "By substitution,
\n" ); document.write( " $\"+100t+-+240+=+80t+\"$
\n" ); document.write( " $\"+20t+=+240+\"$
\n" ); document.write( " $\"+t+=+12+\"$
\n" ); document.write( "This is 12 hrs after the 2nd train leaves at 6 PM + 3 = 9 PM
\n" ); document.write( "The 2nd train catches up with the 1st train at 9 AM the next day
\n" ); document.write( "-----------------
\n" ); document.write( "check answer:
\n" ); document.write( " $\"+d+=+100%2A12+\"$
\n" ); document.write( " $\"+d+=+1200+\"$
\n" ); document.write( "and
\n" ); document.write( " $\"+d+-+240+=+80%2A12+\"$
\n" ); document.write( " $\"+d+=+240+%2B+960+\"$
\n" ); document.write( " $\"+d+=+1200+\"$
\n" ); document.write( "OK \n" ); document.write( "

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