document.write( "Question 17943: A boat travels at the speed of 20 Miles per hour in still water. It travels 48 miles up stream, and then returns to the starting point in a total of five hours. The speed of the current is ____ miles per hour.
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Algebra.Com's Answer #8659 by venugopalramana(3286)\"\" \"About 
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A boat travels at the speed of 20 Miles per hour in still water. It travels 48 miles up stream, and then returns to the starting point in a total of five hours. The speed of the current is ____ miles per hour.
\n" ); document.write( "distance =speed * time..or...time=distance/speed
\n" ); document.write( "Still water speed of boat =20 mph
\n" ); document.write( "let the stream velocity be =x mph
\n" ); document.write( "so its speed upstream =20-x
\n" ); document.write( "its speed down stream =20+x
\n" ); document.write( "distance travelled either way =48 miles
\n" ); document.write( "time taken to travel upstream=48/(20-x)
\n" ); document.write( "time taken to travel down stream =48/(20+x)
\n" ); document.write( "total time of travel =5 hours..hence
\n" ); document.write( "[48/(20-x)]+[48/(20+x)]=5
\n" ); document.write( "48[(20+x+20-x)/((20-x)(20+x))]=5
\n" ); document.write( "48*40=5(20^2-x^2)=2000-5x^2
\n" ); document.write( "5x^2=2000-1920=8=
\n" ); document.write( "x^2=80/5=16
\n" ); document.write( "x=4 mph
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