document.write( "Question 813577: a boat takes 9 hrs to travel from A to B upstream. if river current is 3 km/hr , how long will it take to travel down stream between B and A? \n" ); document.write( "
Algebra.Com's Answer #489910 by ankor@dixie-net.com(22740)\"\" \"About 
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boat takes 9 hrs to travel from A to B upstream.
\n" ); document.write( " if river current is 3 km/hr, how long will it take to travel down stream between B and A?
\n" ); document.write( ":
\n" ); document.write( "I think we need to know the A to B distance
\n" ); document.write( "Let's assume the distance from A to B = 180 mi
\n" ); document.write( "Let s = boat speed in still water
\n" ); document.write( "then
\n" ); document.write( "(s-3) = effective speed upstream (A to B)
\n" ); document.write( "Find s
\n" ); document.write( "9(s - 3) = 180
\n" ); document.write( "simplify, divide by 9
\n" ); document.write( "s - 3 = 20
\n" ); document.write( "s = 20 + 3
\n" ); document.write( "s = 23 mph speed in still water
\n" ); document.write( ":
\n" ); document.write( "(s+3) = effective speed downstream (B to A)
\n" ); document.write( "Let t = time required to go downstream
\n" ); document.write( "t(23 + 3 ) = 180
\n" ); document.write( "26t = 180
\n" ); document.write( "t = 180/26
\n" ); document.write( "t = 6.923 hrs to go downstream (B to A)
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