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The speed of boat upstream and speed of boat downstream are 7 km/h and 13 km/h, respectively. Then the speed of stream and the speed of boat in still water is ?
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- 10 km/h and 3 km/h
- 15 km/h and 9 km/h
- 20 km/h and 6 km/h
- 40 km/h and 12 km/h
Correct Option: A
Rate in still water=[(1/2)(u+v)] km/h
Rate of current=[(1/2)(u-v)] km/h
where u= speed of boat in downstream
v=speed of boat in upstream
Speed of boat in still water=[(1/2)(7+13)] =10 km/h
Speed of the stream =[(1/2)(13-7)]=3 km/h
