A patrol boat took 2.5 h for a round trip 12 km upriver and 12 km back. The speed of the current 2 km/h. What was the speed of the boat in still water?

Answer 1

Since time = distance/speed, we have
12/(x-2) + 12/(x+2) = 5/2
x=10

check:
12 km upstream at 8 km/hr = 1.5 hr
12 km downstream at 12 km/hr = 1 hr
total tiome: 2.5 hr

Answer 2

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