document.write( "Question 133442: A boat traveled 210 miles downstream and back. The trip downstream took 10 hours. The trip back
\n" ); document.write( "took 70 hours. What is the speed of the boat in still water? What is the speed of the current? \n" ); document.write( "

Algebra.Com's Answer #97615 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
Let $\"c\"$ = speed of the current
\n" ); document.write( "Let $\"b\"$ = speed of the boat
\n" ); document.write( "I'm not sure what \"210 mi downstream and back\" means
\n" ); document.write( "I'm assuming it means 105 mi one way and 105 back
\n" ); document.write( "(distance traveled against current) = (distance travelled with current)
\n" ); document.write( " $\"d+=+210%2F2\"$
\n" ); document.write( " $\"d+=+105\"$ mi
\n" ); document.write( "For downstream:
\n" ); document.write( " $\"105%2F10+=+10.5\"$ mi/hr
\n" ); document.write( "For upstream:
\n" ); document.write( " $\"105%2F70+=+1.5\"$ mi/hr
\n" ); document.write( " $\"b+%2B+c+=+10.5\"$
\n" ); document.write( " $\"b+-+c+=+1.5\"$
\n" ); document.write( "Add these
\n" ); document.write( " $\"2b+=+12\"$
\n" ); document.write( " $\"b+=+6\"$ mi/hr
\n" ); document.write( " $\"b+-+c+=+1.5\"$
\n" ); document.write( " $\"6+-+c+=+1.5\"$
\n" ); document.write( " $\"c+=+4.5\"$ mi/hr
\n" ); document.write( "The speed of the boat in still water is 6 mi/hr
\n" ); document.write( "The speed of the current is 4.5 mi/hr
\n" ); document.write( "check answers:
\n" ); document.write( " $\"%28b+%2B+c%29%2A10+=+%28b+-+c%29%2A70\"$
\n" ); document.write( " $\"%286+%2B+4.5%29%2A10+=+%286+-+4.5%29%2A70\"$
\n" ); document.write( " $\"105+=+105\"$
\n" ); document.write( "OK \n" ); document.write( "

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