A motorboat travels 222 km in 6 hours going upstream.
Rate = distance/time = 222/6 = 37 km/hr
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It travels 390 km going downstream in the same amount of time.
Rate = distance/time = 390/6 = 65 km/hr
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What is the rate of the boat in still water and what is the rate of the current?
Equations:
Upstream: b-c = 37 km/hr
Downstrm: b+c = 65 km/hr
Add and solve for "b":
(2)b = 102 km/hr
b = 51 km/hr (speed of the boat in still water)
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Solve for "c":
b+c = 65
51 + c = 65
c = 14 km/hr (speed of the current)