The current of a stream runs at the rate of 4 km an hour.

The current of a stream runs at the rate of 4 km an hour. A boat goes 6 km and comes back to the starting point in 2 hours. The speed of the boat in still water is

Let the speed of boat in still water be y kmph.
According to question ,

⇒	6	+	6	= 2
	y + 4		y - 4

⇒ 6		y - 4 + y + 4		= 2
		(y + 4)(y - 4)

⇒ 6y = y² – 16
⇒ y² – 6y – 16 = 0
⇒ y² – 8y + 2y – 16 = 0
⇒ y (y – 8) + 2 (y – 8) = 0
⇒ (y + 2) (y – 8) = 0
⇒ y = 8 kmph and y ≠ – 2 kmph