A man can row 30 km downstream and return in a total of

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A man can row 30 km downstream and return in a total of 8 hours. If the speed of the boat in still water is four times the speed of the current, then the speed of the current is

1. 1 km/hour
2. 2 km/hour
3. 4 km/hour
4. 3 km/hour

Correct Option: B

Let the speed of stream be k kmph, then speed of boat in still water = 4k kmph
∴ Rate downstream = 4k + k = 5k kmph
Rate upstream = 4k – k = 3k kmph
From the question ,

⇒	30	+	30	= 8 ⇒	10	+	6	= 8
	3k		5k		k		k

⇒	16	= 8 ⇒ k =	16	= 2 kmph
	k		8