Question

A boat moves with 4km/h relative to water in a river flowing with speed 2km/h.The time taken by boat to go 1km upstream and return back to its inital postion in

Answer 1

Speed of boat upstream = 4km/h-2km/h=2km/h

Time = distance/speed=1/2 hours

Therefore answer will be 30minutes

Hope it helps !!!!!!

Answer 2

Answer: 40 min

Speed is the rate at which an object is moving. Speed is a scalar quantity that refers to "how fast an object is moving". An object with no movement at all has a zero speed.

Speed = distance/time

Let the speed of boat be a = 4km/hr

The speed of water/stream be b = 2km/hr

Then the speed of boat in upstream = 4km/h - 2km/h = 2 km/h

For 1 km upstream is,

Time = Distance/ time

$= \frac{1km}{2km/hr}$

$= \frac{1}{2}hr = 30minutes$

To return back, the boat will be on downstream, then the relative speed is,

The speed of boat in downstream = 4km/h + 2km/h = 6 km/h

Time = Distance/ time

$= \frac{1km}{6km/hr}$

$= \frac{1}{6}hr = 10minutes$

Hence it will take 40 min to travel up and down.