Question 589266
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Use <i>distance</i> equals <i>rate</i> times <i>time</i>, from which you can derive <i>rate</i> equals <i>distance</i> divided by <i>time</i>.


To go downstream it takes 1.25 (1 hour 15 minutes is 1 and 1 quarter hour) hours to go 10 miles.  10 divided by 1.25 is 8, so the rate of the boat in still water PLUS the rate of the current is 8 miles per hour.


To go upstream it takes 4 hours to go 10 miles.  10 divided by 4 is 2.5, so the rate of the boat in still water MINUS the rate of the current is 2.5 miles per hour.


Set up your 2X2 system of equations:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ r\ +\ r_c\ =\ 8]


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ r\ -\ r_c\ =\ 2.5]


Use the elimination method to solve for *[tex \LARGE \left(r,\,r_c\right)]


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