SOLUTION: THE CURRENT IN A RIVER IS 4MPH. A BOAT MOTORS 6 MILES UPSTREAM IN THE SAME TIME IT TAKES TO GO 12 MILES DOWNSTREAM. SPEED OF BOAT IN STILL WATER?

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Question 283714: THE CURRENT IN A RIVER IS 4MPH. A BOAT MOTORS 6 MILES UPSTREAM IN THE SAME TIME IT TAKES TO GO 12 MILES DOWNSTREAM. SPEED OF BOAT IN STILL WATER?
Found 3 solutions by mananth, richwmiller, stanbon:
Answer by mananth(16946)   (Show Source):
You can put this solution on YOUR website!
Let speed of boat in still water be x
Speed upstream will be x-4
Speed of boat down stream will be x+4
Time upstream = 6/ x-4 ( Time = distance / rate)
Time downstream = 12/x+4
Both these times are same
6/x-4 = 12 / x+4
6(x+4)=12(x-4)
6x+24=12x-48
6x=72
x= 12 mph the speed of boat in still water

Answer by richwmiller(17219)   (Show Source):
You can put this solution on YOUR website!
Two questions.
How is this a rate of work problem?
Why are you shouting? When the ringing in my ears stops, I'll answer the problem.

Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website!
THE CURRENT IN A RIVER IS 4MPH. A BOAT MOTORS 6 MILES UPSTREAM IN THE SAME TIME IT TAKES TO GO 12 MILES DOWNSTREAM. SPEED OF BOAT IN STILL WATER?
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Upstream DATA:
distance = 6 miles ; rate = b-4 mph ; time = 6/(b-4) hrs
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Downstream DATA:
distance = 12 miles ; rate = b+4 mph ; time = 12(b+4) hrs
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Equation:
time up = time down
6/(b-4) = 12/(b+4)
1/(b-4) = 2/(b+4)
b+4 = 2(b-4)
b+4 = 2b-8
b = 12 mph (boat speed in still water)
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Cheers,
Stan H.