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 ?

Explanation

We are given
`v _(m) = 4 km h ^(-1) , v _(r) = 3 km h ^(-1)` and which of river `OA = 1 km `
We are to calculate, time taken to cross river and distance travelled along river to each other bank. We know that, time `= ("distance")/(" speed")`
`implies i = (OA)/( v _(m)) = (1)/(4) = 0. 25 h.`
Distance `AB = v _(r) xx t = 3 xx 0.25 = 0. 75 km.`