document.write( "Question 161390: The speed of a stream is 4mph. If a boat travels 80 miles downstream in the same time that it takes to travel 40 miles upstream, what is the speed of the boat in still water? \n" ); document.write( "
Algebra.Com's Answer #118943 by checkley77(12844)\"\" \"About 
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D=RT
\n" ); document.write( "80=(D+4)T
\n" ); document.write( "40=(D-4)T
\n" ); document.write( "SEEING AS THE TIMES ARE THE SAME WE HAVE:
\n" ); document.write( "80/(D+4)=40/(D-4)
\n" ); document.write( "80(D-4)=40(D+4)
\n" ); document.write( "80D-320=40D+160
\n" ); document.write( "80D-40D=160+320
\n" ); document.write( "40D=480
\n" ); document.write( "D=480/40
\n" ); document.write( "D=12 MPH FOR THE CURRENT.
\n" ); document.write( "PROOF;
\n" ); document.write( "80/(12+4)=40/(12-4)
\n" ); document.write( "80/16=40/8
\n" ); document.write( "16*40=80*8
\n" ); document.write( "640=640
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\n" ); document.write( "Hi Thank you for your time. One that I simply cannot get is: An airplane
\n" ); document.write( "travels 600 miles against the wind in 4 hrs. and makes the return trip with the
\n" ); document.write( "same wind in 2 hrs. Find the rate of the wind. The answer is either: 75, 150,
\n" ); document.write( "225, or 300mph. I can't seem to get the formula and it is driving me crazy!
\n" ); document.write( "Can you help?
\n" ); document.write( "D=R*T
\n" ); document.write( "600=R*4
\n" ); document.write( "R=600/4=150 MPH AGAINST THE WIND.
\n" ); document.write( "600=R*2
\n" ); document.write( "R=600/2=300 MPH WITH THE WIND.
\n" ); document.write( "(300-150)/2=150/2=75 MPH IS THE SPEED OF THE WIND.\r
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