document.write( "Question 1057326: Carol requires 3 hours to go downstream 21 miles in her motorized boat. Her return trip upstream requires 3 1/2 hours. Assuming that Carol's boat motor runs at a constant pace, find the speed of her boat in still water. \n" ); document.write( "

Algebra.Com's Answer #672369 by josmiceli(19441) $\"\"$ $\"About$

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Let $\"+s+\"$ = the speed of her boat in still water
\n" ); document.write( "Let $\"+c+\"$ = the speed of the current
\n" ); document.write( " $\"+s+%2B+c+\"$ = her speed going downstream
\n" ); document.write( " $\"+s+-+c+\"$ = her speed going upstream
\n" ); document.write( "---------------------------------------------
\n" ); document.write( "Equation for going downstream:
\n" ); document.write( "(1) $\"+21+=+%28+s+%2B+c+%29%2A3+\"$
\n" ); document.write( "Equation for going upstream:
\n" ); document.write( "(2) $\"+21+=+%28+s+-+c+%29%2A3.5+\"$
\n" ); document.write( "---------------------------
\n" ); document.write( "Add the equations:
\n" ); document.write( "(1) $\"+s+%2B+c+=+7+\"$
\n" ); document.write( "(2) $\"+s+-+c+=+6+\"$
\n" ); document.write( "-------------------
\n" ); document.write( " $\"+2s+=+13+\"$
\n" ); document.write( " $\"+s+=+6.5+\"$
\n" ); document.write( "--------------
\n" ); document.write( "the speed of her boat in still water is 6.5 mi/hr
\n" ); document.write( "--------------
\n" ); document.write( "check answer:
\n" ); document.write( "(1) $\"+s+%2B+c+=+7+\"$
\n" ); document.write( "(1) $\"+6.5+%2B+c+=+7+\"$
\n" ); document.write( "(1) $\"+c+=+.5+\"$ mi/hr
\n" ); document.write( "and
\n" ); document.write( "(2) $\"+s+-+c+=+6+\"$
\n" ); document.write( "(2) $\"+6.5+-+c+=+6+\"$
\n" ); document.write( "(2) $\"+c+=+.5+\"$
\n" ); document.write( "OK
\n" ); document.write( " \n" ); document.write( "

\n" );