A man rows to a place 35 km in distant and back in 10 hours

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A man rows to a place 35 km in distant and back in 10 hours 30 minutes. He found that he could row 5 km with the stream in the same time as he can row 4 km against the stream. Find the rate of flow of the stream.:

1. 1 km/hr
2. 0.5 km/hr
3. 0.75 km/hr
4. 1.5 km/hr

Correct Option: C

Suppose Speed of man in still water = p kmph.
Speed of current = q kmph
Rate downstream = (p + q) kmph
Rate upstream = (p – q) kmph
According to the question ,

5	=	4
p + q	=	p - q

⇒ 5p – 5q = 4p + 4q
⇒ p = 5q + 4q = 9q .......( 1 )

Again,	35	+	35	= 10	1	=	21
	p + q		p - q		2		2

Putting the value of p of equation ( 1 ) , we get

⇒	35	+	35	=	21
	9q + q		9q - q		2

⇒	5	+	5	=	3
	10q		8q		2

⇒	1	+	5	= 3
	q		4q

⇒	4 + 5	= 3
	4q

⇒ 9 = 12q

⇒ q =	9	=	3	kmph
	12		4