document.write( "Question 882550: A motorboat maintained a constant speed of 15 mph relative to the water in going 10 miles upstream and then returning. The total time for this trip was 1.5 hours. Use this info to find the speed of the current.\r
\n" ); document.write( "\n" ); document.write( "*PLEASE* help explain how I figure this out! \n" ); document.write( "
Algebra.Com's Answer #532932 by lwsshak3(11628)\"\" \"About 
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A motorboat maintained a constant speed of 15 mph relative to the water in going 10 miles upstream and then returning. The total time for this trip was 1.5 hours. Use this info to find the speed of the current.
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\n" ); document.write( "let x=speed of current
\n" ); document.write( "15+x=speed of boat downstream
\n" ); document.write( "15-x=speed of boat upstream
\n" ); document.write( "travel time=distance/speed
\n" ); document.write( "total travel time=travel time upstream+travel time downstream
\n" ); document.write( "1.5=10/(15-x)+10/(15+x)
\n" ); document.write( "lcd:(15-x)(15+x)
\n" ); document.write( "1.5*(15-x)(15+x)=10(15+x)+10(15-x)
\n" ); document.write( "1.5(15^2-x^2)=150+10x+150-10x
\n" ); document.write( "1.5(225-x^2)=300
\n" ); document.write( "(225-x^2)=200
\n" ); document.write( "x^2=25
\n" ); document.write( "x=±5
\n" ); document.write( "speed of current=5 mph \n" ); document.write( "
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