Question 518135
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If she goes 3 miles in 15 minutes, which is 1/4 hour, she must be going 12 miles per hour.  If she goes 3 miles in 20 minutes, or 1/3 hour, she must be going 9 miles per hour.  Her still water speed plus the current is the downstream trip (current aided) so *[tex \Large r\ +\ r_c\ =\ 12] and the upstream trip is *[tex \Large r\ -\ r_c\ =\ 9].


Solve the 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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