document.write( "Question 795399: If a boat can travel 30mph in still water, and can travel 9 miles downstram in the same time it takes 1 mile to go upstream, what is the rate of the rivers current? \n" ); document.write( "
Algebra.Com's Answer #480964 by josmiceli(19441)\"\" \"About 
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Let \"+c+\" = the rate of the current in mi/hr
\n" ); document.write( "\"+30+%2B+c+\" = boat's speed going downstream in mi/hr
\n" ); document.write( "\"+30+-+c+\" = boat's speed going upstream in mi/hr
\n" ); document.write( "Let \"+t+\" = the time in hours for both upstream and downstream
\n" ); document.write( "-----------------------
\n" ); document.write( "Equation for going downstream:
\n" ); document.write( "(1) \"+9+=+%28+30%2B+c+%29%2At+\"
\n" ); document.write( "Equation for going upstream:
\n" ); document.write( "(2) \"+1+=+%28+30+-+c+%29%2At+\"
\n" ); document.write( "--------------------
\n" ); document.write( "(1) \"+9+=+30t+%2B+c%2At+\"
\n" ); document.write( "and
\n" ); document.write( "(2) \"+1+=+30t+-+c%2At+\"
\n" ); document.write( "-------------------
\n" ); document.write( "Add the equations
\n" ); document.write( "\"+10+=+60t+\"
\n" ); document.write( "\"+t+=+1%2F6+\"
\n" ); document.write( "and
\n" ); document.write( "(1) \"+9+=+%28+30%2B+c+%29%2A%281%2F6%29+\"
\n" ); document.write( "(1) \"+54+=+30+%2B+c+\"
\n" ); document.write( "(1) \"+c+=+24+\"
\n" ); document.write( "The rate of the current is 24 mi/hr
\n" ); document.write( "check:
\n" ); document.write( "(2) \"+1+=+%28+30+-+c+%29%2At+\"
\n" ); document.write( "(2) \"+1+=+%28+30+-+24+%29%2A%281%2F6%29+\"
\n" ); document.write( "(2) \"+6+=+6+\"
\n" ); document.write( "and
\n" ); document.write( "(1) \"+9+=+%28+30%2B+c+%29%2At+\"
\n" ); document.write( "(1) \"+9+=+%28+30%2B+24+%29%2A%281%2F6%29+\"
\n" ); document.write( "(1) \"+54+=+54+\"
\n" ); document.write( "OK\r
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