document.write( "Question 193055: Thor's average driving speed is 25 km/hr faster than Kirk's. In the same length of time it takes Thor to drive 279 km, Kirk only drives 204 km. What is Thor's average speed? \n" ); document.write( "

Algebra.Com's Answer #144945 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
Two equations for Kirk and Thor:
\n" ); document.write( " $\"d%5Bk%5D+=+r%5Bk%5D%2At%5Bk%5D\"$
\n" ); document.write( " $\"d%5Bt%5D+=+r%5Bt%5D%2At%5Bt%5D\"$
\n" ); document.write( "given:
\n" ); document.write( " $\"r%5Bt%5D+=+r%5Bk%5D+%2B+25\"$
\n" ); document.write( " $\"t%5Bk%5D+=+t%5Bt%5D\"$ (I'll call them both $\"t\"$ )
\n" ); document.write( " $\"d%5Bt%5D+=+279\"$
\n" ); document.write( " $\"d%5Bk%5D+=+204\"$
\n" ); document.write( "----------------
\n" ); document.write( " $\"d%5Bk%5D+=+r%5Bk%5D%2At%5Bk%5D\"$
\n" ); document.write( "(1) $\"204+=+%28r%5Bt%5D+-+25%29%2At\"$
\n" ); document.write( " $\"d%5Bt%5D+=+r%5Bt%5D%2At%5Bt%5D\"$
\n" ); document.write( "(2) $\"279+=+r%5Bt%5D%2At\"$
\n" ); document.write( "From (1):
\n" ); document.write( "(1) $\"r%5Bt%5D%2At+-+25t+-+204+=+0\"$
\n" ); document.write( "From (2):
\n" ); document.write( "(2) $\"r%5Bt%5D%2At+-+279+=+0\"$
\n" ); document.write( "Subtract (1) from (2):
\n" ); document.write( " $\"25t+-+75+=+0\"$
\n" ); document.write( " $\"25t+=+75\"$
\n" ); document.write( " $\"t+=+3\"$ hrs
\n" ); document.write( "Plug this result into (2)
\n" ); document.write( "2) $\"279+=+r%5Bt%5D%2At\"$
\n" ); document.write( " $\"279+=+r%5Bt%5D%2A3\"$
\n" ); document.write( " $\"r%5Bt%5D+=+93\"$
\n" ); document.write( "Thor's average speed is 93 km/hr
\n" ); document.write( "check answer:
\n" ); document.write( "(1) $\"204+=+%28r%5Bt%5D+-+25%29%2At\"$
\n" ); document.write( " $\"204+=+%2893+-+25%29%2A3\"$
\n" ); document.write( " $\"204+=+68%2A3\"$
\n" ); document.write( " $\"204+=+204\"$
\n" ); document.write( "OK \n" ); document.write( "

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