Question 862389
A person rowed her boat upstream for a distance of 32 mil and then rowed backed to the starting point.  The total time of the trip was 18 hours.  If the rate of the current was 7 mph, find the average of the boat in still water.
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d = distance one way
c = speed of the current = 7
b = boat's speed
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d = r*t
t = d/r
18 = 32/(b-7) + 32/(b+7)
18*(b-7)*(b+7) = 32*(b+7) + 32*(b-7)
9*(b^2 - 49) = 32b
{{{9b^2 - 32b - 49 = 0}}}
*[invoke solve_quadratic_equation 9,-32,-49]
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b =~ 4.7112 mi/hr
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It's not a simple problem.