document.write( "Question 410876: A train left Podunk and traveled west at 70 km/h. Two hours later, another train left Podunk and traveled east at 90km/h. How many hours had the first train traveled when they were 1420 km apart? \n" ); document.write( "

Algebra.Com's Answer #288870 by josmiceli(19441) $\"\"$ $\"About$

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Let $\"d\"$ = distance 2nd train goes when they are 1420 km apart
\n" ); document.write( "The 1st train has gone $\"70%2A2+=+140\"$ km when the 2nd train leaves.
\n" ); document.write( "Both trains travel for the same length of time when 2nd train leaves
\n" ); document.write( "2nd train:
\n" ); document.write( " $\"d%5B2%5D+=+90%2At\"$
\n" ); document.write( "1st train:
\n" ); document.write( " $\"d%5B1%5D+=+70%2At\"$
\n" ); document.write( " $\"d%5B1%5D+%2B+d%5B2%5D+%2B+140+=+1420\"$ km
\n" ); document.write( "By substitution:
\n" ); document.write( " $\"70t+%2B+90t+%2B+140+=+1420\"$
\n" ); document.write( " $\"160t+=+1280\"$
\n" ); document.write( " $\"t+=+8\"$ hrs
\n" ); document.write( "The 1st train traveled $\"8+%2B+2+=+10\"$ hrs
\n" ); document.write( "when they are 1420 km apart
\n" ); document.write( "check answer:
\n" ); document.write( " $\"d%5B1%5D+=+70%2A8\"$
\n" ); document.write( " $\"d%5B1%5D+=+560\"$
\n" ); document.write( " $\"d%5B2%5D+=+90%2A8\"$
\n" ); document.write( " $\"d%5B2%5D+=+720\"$
\n" ); document.write( " $\"d%5B1%5D+%2B+d%5B2%5D+=+560+%2B+720\"$
\n" ); document.write( " $\"d%5B1%5D+%2B+d%5B2%5D+=+1280\"$
\n" ); document.write( " $\"1280+%2B+140+=+1420\"$ \n" ); document.write( "

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