Question 455372
The question is: A river has a current of 3mph. A boat goes 35 miles upstream in the same time as it goes 45 miles downstream. Find the speed of the boat in still water?
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downstream rate = b+3 mph where "b" is boat speed in still water
upstream rate = b-3 mph where "b" is boat speed in still water
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Upstream DATA:
distance = 35 miles ; rate = b-3 mph ; time = d/r = 35/(b-3) hrs.
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Dosnstream DATA:
distance = 45 miles ; rate = b+3 mph ; time = d/r = 45/(b+3)
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Equation:
time up = time down
35/(b-3) = 45/(b+3)
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35b + 105 = 45b - 135
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10b = 240
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b = 24 mph (speed of the boat in still water)
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Cheers,
Stan H.
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