document.write( "Question 332141: a bicyclist rode up a mountain at 12 km/h and then back down at 30 km/h. if a round trip takes 3.5 hours, how long did the ride up take? \n" ); document.write( "

Algebra.Com's Answer #238049 by josmiceli(19441) $\"\"$ $\"About$

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Let $\"t\"$ = time in hours to go uphill
\n" ); document.write( "Then $\"3.5+-+t\"$ will be the time to go downhill
\n" ); document.write( "equation for uphill:
\n" ); document.write( " $\"d+=+r%2At\"$
\n" ); document.write( " $\"d+=+12t\"$ km
\n" ); document.write( "equation for downhill:
\n" ); document.write( " $\"d+=+30%2A%283.5+-+t%29\"$ km
\n" ); document.write( " $\"d+=+105+-+30t\"$ km
\n" ); document.write( "Since both equal $\"d\"$ ,
\n" ); document.write( " $\"12t+=+105+-+30t\"$
\n" ); document.write( " $\"42t+=+105\"$
\n" ); document.write( " $\"t+=+2.5\"$
\n" ); document.write( "The trip up took 2.5 hrs
\n" ); document.write( "check:
\n" ); document.write( " $\"d+=+30%2A%283.5+-+t%29\"$ km
\n" ); document.write( " $\"d+=+30%2A%283.5+-+2.5%29\"$ km
\n" ); document.write( " $\"d+=+105+-+75\"$
\n" ); document.write( " $\"d+=+30\"$ km
\n" ); document.write( "and
\n" ); document.write( " $\"d+=+12t\"$ km
\n" ); document.write( " $\"d+=+12%2A2.5\"$
\n" ); document.write( " $\"d+=+30\"$ km
\n" ); document.write( "OK \n" ); document.write( "

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