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A boat running down stream covers a distance of 16km in two hours .while covering a same distance upstream it takes 4hours .what is the speed of the boat in still water?"

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by jayantu

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by jayantu

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time= 2hr

down stream speed= 16/2= 8km/hr

upstream speed=16/4= 4km/hr

boat's speed=x km/hr

river speed= y km/hr

x+y=8

x=8-y ....(1)

x-y=4

x=y+4.....(2)

8-y=y+4

8=2y+4

2y=4

y=4/2=2 km/hr

x+y=8 ...so x+2=8

x=6

speed of the boat= 6km/hr