The speed of a boat in still water is 10 km/hr. It covers

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The speed of a boat in still water is 10 km/hr. It covers (upstream) a distance of 45 km in 6 hours. The speed (in km/hr) of the stream is

1. 2.5
2. 3
3. 3.5
4. 4

Correct Option: A

Given that , Distance = 45 km and Time = 6 hours
The speed of a boat in still water = 10 km/hr
As we know that ,

Upstream speed of boat =	Distance	=	45	=	15
	Time		6		2

Upstream speed of boat = 7.5 kmph
∴ Speed of current = 10 – 7.5 = 2.5 kmph
We can find the required answer with the help of given formula :
Here , Speed of Boat = 10 km/hr
Let, p = Speed of Boat (Down Stream)

q = Speed of Boat (Up Stream) =	45	kmph
	6

∴ Speed of Boat =	p + q
	2

10 =	p +	45
		6

		2

120 = 6p + 45 ⇒ 6p = 75
p = 75 /6 = 25 / 2 km/hr

Speed of Stream =	p - q
	2

Speed of Stream =	1		25	-	45
	2		2		6

Speed of Stream =	1		75 - 45
	2		6

∴ Speed of Stream =	5	= 2.5 km/hr
	2