document.write( "Question 760024: A boat takes a trip upriver against the current in 6 hours. Coming back down river, the boat
\n" ); document.write( "can travel 6 mph faster and makes the trip in 4 hours. What is the speed of the boat in still
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Algebra.Com's Answer #462373 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
Let $\"+s+\"$ = the speed of the boat in still water in mi/hr
\n" ); document.write( "Let $\"+c+\"$ = the speed of the current in mi/hr
\n" ); document.write( " $\"+s+-+c+\"$ = the speed of the boat going upriver
\n" ); document.write( " $\"+s+%2B+c+\"$ = the speed of the boat going downriver
\n" ); document.write( "Let $\"+d+\"$ = the one-way distance the boat travels
\n" ); document.write( "------------------
\n" ); document.write( "Going upriver:
\n" ); document.write( "(1) $\"+d+=+%28+s+-+c+%29%2A6+\"$
\n" ); document.write( "Going downriver:
\n" ); document.write( "(2) $\"+d+=+%28+s+%2B+c+%29%2A4+\"$
\n" ); document.write( "and, also given:
\n" ); document.write( "(3) $\"+s+%2B+c+=+s+-+c+%2B+6+\"$
\n" ); document.write( "---------------------
\n" ); document.write( "(3) $\"+c+=+-c+%2B+6+\"$
\n" ); document.write( "(3) $\"+2c+=+6+\"$
\n" ); document.write( "(3) $\"+c+=+3+\"$ mi/hr
\n" ); document.write( "-------------------
\n" ); document.write( "By substitution:
\n" ); document.write( "(2) $\"+%28+s-c+%29%2A6+=+%28+s+%2B+c+%29%2A4+\"$
\n" ); document.write( "(2) $\"+%28+s-3+%29%2A6+=+%28+s+%2B+3+%29%2A4+\"$
\n" ); document.write( "(2) $\"+6s+-+18+=+4s+%2B+12+\"$
\n" ); document.write( "(2) $\"+2s+=+30+\"$
\n" ); document.write( "(2) $\"+s+=+15+\"$
\n" ); document.write( "The speed of the boat in still water is 15 mi/hr
\n" ); document.write( "check:
\n" ); document.write( "(1) $\"+d+=+%28+s+-+c+%29%2A6+\"$
\n" ); document.write( "(1) $\"+d+=+%28+15+-+3+%29%2A6+\"$
\n" ); document.write( "(1) $\"+d+=+72+\"$ mi
\n" ); document.write( "and
\n" ); document.write( "(2) $\"+d+=+%28+s+%2B+c+%29%2A4+\"$
\n" ); document.write( "(2) $\"+d+=+%28+15+%2B+3+%29%2A4+\"$
\n" ); document.write( "(2) $\"+d+=+72+\"$ mi
\n" ); document.write( "OK
\n" ); document.write( " \n" ); document.write( "

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