A boat goes 6 km an hour in still water, but takes thrice

A boat goes 6 km an hour in still water, but takes thrice as much time in going the same distance against the current. The speed of the current (in km/hour) is :

Let the speed of the current be y kmph.
∴ speed of boat = 6 kmph.
According to the question,

6	= 3
6 - y

⇒ 18 – 3y = 6
⇒ 3y = 18 – 6 ⇒ 3y = 12

⇒ y =	12	= 4kmph
	3

We can find the required answer with the help of given formula :
Here, Speed of boat = 6 km/hr
t₁ = 3k, t₂ = k

	Speed of Boat	=	t₁ + t₂
	Speed of Stream		t₁ - t₂

	6	=	3k + k
	Speed of Stream		3k - k

Speed of current = 3 km/hr