SOLUTION: the current in a stream moves at a speed of 3 mph. Aboat travels 45 mi upstream and 45 mi downstream in a total time of 8 hr. what is the speed of the boat in still water?
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Question 250972: the current in a stream moves at a speed of 3 mph. Aboat travels 45 mi upstream and 45 mi downstream in a total time of 8 hr. what is the speed of the boat in still water?
Answer by checkley77(12844) (Show Source): You can put this solution on YOUR website!
D=RT
R=D/T
(R+3)(R-3)8=2*45
8(R^2-9)=90
8R^2-72=90
8R^2=90+72
8R^2=162
R^2=162/8
R^2=20.25
R=SQRT20.25
R=4.5 MPH IS THE SPEED OF THE BOAT IN STILL WATER.
PROOF:
(4.5+3)(4.5-3)*8=2*45
7.5*1.5*8=90
90=90
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