You can
put this solution on YOUR website!The speed of a mototboat in still water is 15 mi/hr. If it takes the motorboat the same time to go 15 mi upstream the river as it takes to go 30 mi
downstream, what is the speed of the current?
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Let the rate of the current be "x":
Upstream DATA:
Distance = 15 mi ; rate = 15-x ; time = d/r = 15(15-x) mph
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Downstream DATA:
Distance = 30 mi ; rate = 15+x ; time = d/r = 30/(15+x) mph
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EQUATION:
time up = time down
15/(15-x) = 30/(15+x)
Divide both sides by 15 to get:
1/(15-x) = 2/(15+x)
15+x = 2(15-x)
15+x = 30-2x
3x=15
x=5 mph
The speed of the current is 5 mph
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Cheers,
Stan H.
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