<PRE><B>Question 1110188</B>
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A boat goes 30km upstream and 44kms downstream in 10hrs.
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r, boat speed without current
c, speed of current

time, {{{30/(r-c)+44/(r+c)=10}}}



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In 13hrs it can go 40kms upstream and 55kms downstream.
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{{{40/(r-c)+55/(r+c)=13}}}


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The speed of the boat in still water is?
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I did not show a finished solution.  Only showed a possible way to start analyzing the description.  Two equations in the two unknown variables, r and c.</PRE>