A cruise boat travels 72 miles down stream in two hours and

A cruise boat travels 72 miles down stream in two hours and returns upstream in 6 hours. Find the rate of the stream.
D=RT so R=D/T 72/2=36 72/6=12 36-12=24 (speed of boat on still water?)

Solution

Down stream DATA:
distance = 72 miles ; time = 2 hrs: rate = d/t = 72/2 = 36 mph
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Up stream DATA:
distance = 72 miles ; time = 6 hrs. rate = 72/6 = 12 mph
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Equations
Down stream rate: b + c = 36 mph
Upstream rate...: b - c = 12
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Add to get 2b = 48
b = 24 mph (rate of the boat in still water)
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Substitute to find \"c\":
b+c = 24 + c = 36
c = 36-24 = 12 mph (speed of the current)