Question 724624: A motorboat takes 3 hrs to make a trip downstream with a 6 mph current. Returning from the trip, on the same current, it took 5 hrs. How do I calculate the speed of the boat that's still in the water?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! A motorboat takes 3 hrs to make a trip downstream with a 6 mph current. Returning from the trip, on the same current, it took 5 hrs. How do I calculate the speed of the boat in still in water?
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Let speed in still water be "b":
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Downstream DATA:
time = 3 hrs ; rate = b+6 mph ; distance = r*t = 3(b+6) miles
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Upstream DATA:
time = 5 hrs ; rate = b-6 mph ; distance = r*t = 5(b-6) miles
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Equation:
distance down = distance up
3(b+6) = 5(b-6)
3b + 18 = 5b - 30
2b = 48
b = 24 mph (speed of the boat in still water)
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Cheers,
Stan H.
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