document.write( "Question 903301: A motorboat maintains a constant speed of 15 mph relative to the water in a river. The boat went 10 miles upstream and back in a total of 1.5 hours. What is the speed of the current (in mph)? \n" ); document.write( "
Algebra.Com's Answer #547947 by mananth(16946)\"\" \"About 
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boat speed = 15 km/h
\n" ); document.write( "current speed = x km/h
\n" ); document.write( "
\n" ); document.write( "against current = 15 - x
\n" ); document.write( "with current = 15 + x
\n" ); document.write( "
\n" ); document.write( "Total distance = 10 miles Total Time= 1.50 hours
\n" ); document.write( "Time upstream + time downstream = 1.5 hours
\n" ); document.write( "
\n" ); document.write( "10 /( 15 - x )+ 10 /( 15 + x )= 1.5
\n" ); document.write( "10 ( 15 + x )+ 10 ( 15 - x )= 1.50 ( 225 - 1 X^2 )
\n" ); document.write( "150 + 10 x + 150 -10 x = 337.5 - 1.5 X^2
\n" ); document.write( "300 - -337.5 = -1.5 X^2
\n" ); document.write( "-37.5 = -1.5 X^2
\n" ); document.write( "-1.5 X^2= -37.5
\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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