a man can swim with a speed of 4km/hr in still water.how long does he take to cross a river 1km wide,if the river flows steadily at 3km/hr and he makes his strokes normal to the river current?how far in the river does he go,when he reaches the other bank?

speed of man=4km/hwidth=1kmsince, time=distance/velocity time=1/4t=0.25hournow convet into minutes for easy callcuationt=0.25.60=15minutesvelocity of water=3km\hournow, due to motion of river water the man will reach the other bank of the river. distance=speed x timed=3x0.25=0.75kmdistance= 750m

So basically all u need to use here is speed = distance /time formula.So the width of river = 3kmSpeed of man is 4km/hSo time taken by man to reach other end= width of river /speed of man.That is.... 1km/4km/h = 1/4 h= 15 minutes.Now the distance travelled by him is nothing but time taken by him * speed of river = 1/4h * 3km/h = 3/4km = 750 m