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A man can swim with a speed of 4.0 km/h...

A man can swim with a speed of 4.0 km/h in still water . How long does he take to cross a river 1.0 km wide if the river flows steadily at 3.0 km/h and he makes his strokes normal to the river current ? How far down the river does he go when he reaches the other bank ?

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(a) time taken `t=(AB)/(v_(m))=(1)/(4)hr=15` min.
(b) The distance travelled along the river during its crossing is
`BC=v_(R)xxt=3xx(1)/(4)=0.75km`
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