<PRE><B>Question 536125</B>
D=RT and remember these problems often contain two situations.  This one contains two situations.&lt;P&gt;
1.  D = rt where rate is r+8km/hr because it is moving with the current so the current adds to the speed.  t = 2.  Thus D=2(r+8)&lt;P&gt;
2.  The return trip was against the current, so the current works against the boat&#39;s speed (subtracts from it.)  rate is r-8 and t=3.  Thus D=3(r-8)&lt;P&gt;

3.  Because the boat traveled the same distance each time, those two equations both equal the same D, and thus are both equal to each other.&lt;P&gt;

2(r+8)=3(r-8)  (Multiply the numbers by each term in ().)  2r+16=3r-24&lt;P&gt;
Subtract 2r from each side, add 24 to each side.&lt;P&gt;
40=r.  &lt;P&gt;
The rate of the boat in still air (without any current working with or against it) is 40 km/hr.
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