document.write( "Question 621317: A boat travels 50 miles downstream in the same time that it takes to go 30 miles upstream. The speed of the boat in still water is a constant 36 miles per hour. Then, in mph, the speed of the stream is \n" ); document.write( "

Algebra.Com's Answer #390678 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
Let $\"+s+\"$ = the speed of the stream
\n" ); document.write( "Let $\"+t+\"$ = the time to go upstream and downstream
\n" ); document.write( "Going downstream:
\n" ); document.write( "(1) $\"+50+=+%28+36+%2B+s+%29%2At+\"$
\n" ); document.write( "Going upstream:
\n" ); document.write( "(2) $\"+30+=+%28+36+-+s+%29%2At+\"$
\n" ); document.write( "--------------------
\n" ); document.write( "(1) $\"+50+=+36t+%2B+s%2At+\"$
\n" ); document.write( "(2) $\"+30+=+36t+-+s%2At+\"$
\n" ); document.write( "Add the equations
\n" ); document.write( " $\"+80+=+72t+\"$
\n" ); document.write( " $\"+t+=+80%2F72+\"$
\n" ); document.write( " $\"+t+=+10%2F9+\"$ hrs
\n" ); document.write( "and
\n" ); document.write( "(1) $\"+50+=+%28+36+%2B+s+%29%2A%2810%2F9%29+\"$
\n" ); document.write( "(1) $\"+9%2A50+=+10%2A%28+36+%2B+s+%29+\"$
\n" ); document.write( "(1) $\"+45+=+36+%2B+s+\"$
\n" ); document.write( "(1) $\"+s+=+9+\"$
\n" ); document.write( "The speed of the stream is 9 mi/hr
\n" ); document.write( "check:
\n" ); document.write( "(2) $\"+30+=+%28+36+-+s+%29%2At+\"$
\n" ); document.write( "(2) $\"+30+=+%28+36+-+9+%29%2A%2810%2F9%29+\"$
\n" ); document.write( "(2) $\"+30+=+27%2A%2810%2F9%29+\"$
\n" ); document.write( "(2) $\"+270+=+270+\"$
\n" ); document.write( "OK \n" ); document.write( "

\n" );