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Unformatted text preview: 19.BOATS AND STREAMS IMPORTANT FACTS AND FORMULAE 1.In water ,the direction along the stream is called downstream and ,the direction against the stream is called upstream. 2.If the speed of a boat in still water is u km/hr and the speed of the stream is v km/hr,then: speed downstream=(u+v)km/hr. speed upstream=(uv)km/hr . 3.If the speed downstream is a km/hr and the speed upstream is b km/hr,then : speed in still water=1/2(a+b)km/hr rate of stream=1/2(ab)km/hr SOLVED EXAMPLES EX.1.A man can row upstream at 7 kmph and downstream at 10kmph.find man’s rate in still water and the rate of current. Sol. Rate in still water=1/2(10+7)km/hr=8.5 km/hr. Rate of current=1/2(107)km/hr=1.5 km/hr. EX.2. A man takes 3 hours 45 minutes to row a boat 15 km downstream of a river and 2hours30minutes to cover a distance of 5km upstream. find the speed of the river current in km/hr. Sol. rate downstream=(15/3 ¾)km/hr=(15*4/15)km/hr=4km/hr....
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This note was uploaded on 08/13/2011 for the course FSD 011 taught by Professor Vinh during the Spring '11 term at Beacon FL.
 Spring '11
 vinh

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