Question 1130788
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Let *[tex \Large r_b] represent the speed of the boat in still water.


Let *[tex \Large r_c] represent the speed of the river current


The distance is a constant 56 miles.  Time for the downstream (with the current) trip is 4 hours, time for the upstream (against the current) trip is 7 hours (4 + 3).


Rate of speed of the boat considering the current is *[tex \Large r_b\ +\ r_c] downstream and *[tex \Large r_b\ -\ r_c] upstream.  Then since rate times time equals distance:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 4(r_b\,+\,r_c)\ =\ 56]


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 7(r_b\ -\ r_c)\ =\ 56]


Solve the system for *[tex \Large r_c]
								
								
John
*[tex \LARGE e^{i\pi}\ +\ 1\ =\ 0]
My calculator said it, I believe it, that settles it
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*[tex \Large \ \
*[tex \LARGE \ \ \ \ \ \ \ \ \ \  
								
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