Asked by anj

The speed of a stream is 3 km/h. A boat travels 25 km upstream in the same time it takes to travel 35 km downstream. What is the speed of the boat in still water?
Answered by Reiny
speed of boat in still water ---> x km/h

time to go 25km upstream = 25/(x-3)
time to go 35 km downstream = 35/(x+3)

but those two times are supposed to be equal, so ..
25/(x-3) = 35/(x+3)

cross-multiply, then solve for x
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