Question 637732
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Let *[tex \LARGE r] represent the speed of the boat in still water.  Let *[tex \LARGE r_c] represent the speed of the current.  Downstream the boat travels at *[tex \LARGE r\ +\ r_c] miles per hour.  Upstream the boat travels at *[tex \LARGE r\ -\ r_c] miles per hour.


Distance equals rate times time, so


Downstream trip:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 14(r\ +\ r_c)\ =\ 252]


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 14r\ +\ 14r_c\ =\ 252]


Upstream trip:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 21(r\ -\ r_c)\ =\ 252]


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 21r\ -\ 21r_c\ =\ 252]


Solve the 2X2 system for *[tex \LARGE r] and *[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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