document.write( "Question 1116608: A boat travels 9 km upstream and 9 km back. The time for the round trip is 3 hrs. The speed of the stream is 5 km/hr. What is the speed of the boat in still water? \n" ); document.write( "

Algebra.Com's Answer #731491 by josgarithmetic(39617) $\"\"$ $\"About$

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r, boat speed if no stream current\r
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document.write( "           SPEED       TIME             DISTANCE\r\n" );
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document.write( "UP          r-5                   9\r\n" );
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document.write( "DOWN        r+5                   9\r\n" );
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document.write( "TOTAL                  3\r\n" );
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\n" ); document.write( "\n" ); document.write( " $\"highlight_green%289%2F%28r-5%29%2B9%2F%28r%2B5%29=3%29\"$ \r
\n" ); document.write( "\n" ); document.write( "-\r
\n" ); document.write( "\n" ); document.write( " $\"3%2F%28r-5%29%2B3%2F%28r%2B5%29=1\"$ \r
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\n" ); document.write( "\n" ); document.write( " $\"3%28r%2B5%29%2B3%28r-5%29=r%5E2-25\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"6r=r%5E2-25\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"r%5E2-25-6r=0\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"r%5E2-6r-25=0\"$ \r
\n" ); document.write( "\n" ); document.write( "--\r
\n" ); document.write( "\n" ); document.write( "discriminant $\"36%2B4%2A25=136=4%2A34\"$ \r
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\n" ); document.write( "\n" ); document.write( " $\"r=%286%2B2%2Asqrt%2834%29%29%2F2\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"highlight%28r=3%2Bsqrt%2834%29%29\"$ \r
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\n" ); document.write( "\n" ); document.write( "8.8 km/hour \n" ); document.write( "

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