Question

A man can swim with a speed of km per hour in still water . How long does he take to cross a river 1km wide, if the river flows steadily at 3 km per hour and he makes his strokes normal to the river current? How far in the river does he go, when he reaches the other bank

Answer 1

HEY DEAR ...

Let velocity of river be Vr = 3km/h

the time (t) taken to cross the river will be:- 

t= river width/speed of man   (time=dis/speed)

t=1/4 hour

 

Now dis=speed*time

distance moved in time t= Vr*t= 3km/h*1/4h=3/4 km

 

So distance travelled by man = 3/4km=750 meter

HOPE , IT HELPS ...

Answer 2

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Speed of the man,

vm = 4 km/h

Width of the river = 1 km

Time taken to cross the river

= Width of the river/ speed of the river

= 1/4 h

=15 min

Speed of the river, vr = 3 km/h

Distance covered with flow of the river

Distance covered with flow of the river = vr × t

= vr × t = 3× 1/4 = 3/4 km

= 3/4 × 1000 = 750 m

I hope, this will help you

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