SOLUTION: The current of a river is 2 miles per hour. A boat travels to a point 8 miles upstream and back again in 3 hours. What is the speed of the boat in still water?

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Question 419040: The current of a river is 2 miles per hour. A boat travels to a point 8 miles upstream and back again in 3 hours. What is the speed of the boat in still water?
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
speed in still water = x
current speed 2

upstream speed = x-2
downstream speed = x+2

Distance= 16 miles

Time upstream + time downstream = 3hours
t=d/r
............
16/(x+2)+16/(x-2)=3
LCD = (x-2)(x +2)
16*(x-2)+16(x+2)=3
16x-32+ 16x+32=3(X^2-4)
32x=3X^2-12
3X^2-32 x-12=0
Use the quadratic formula
b^2-4ac= 1168
x=(32+sqrt(1168))/6
11.03 mph speed in still water