SOLUTION: a person rowed her boat upstream a distance of 5 miles and then back to the starting point. The total time of the trip was 6 hours. If the rate of the current was 2 miles per hour,

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Question 446098: a person rowed her boat upstream a distance of 5 miles and then back to the starting point. The total time of the trip was 6 hours. If the rate of the current was 2 miles per hour, find the average speed of the boat in still water
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
Boat speed x
current speed 2

against current x-2 mph
with current x+ 2 mph

Distance= 5 miles

Time against + time with = 6 hours
t=d/r
Find the roots of the equation by quadratic formula

a= 6, b= -10, c= -24,

b^2-4ac=100+576
b^2-4ac=676
sqrt(676)=26
x=%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F%282a%29
x1=%28-b%2Bsqrt%28b%5E2-4ac%29%29%2F%282a%29
x1=(10 +26)/12
x1=3
x2=(10-26)/12
x2= -1.33
Ignore negative value
3 mph speed of boat in still water