A man crosses a river in a boat if he crosses the river in minimum time he take 10min with a drift 120metre if he crosses the river taking shortest path he takes 12.5min find the width of the river

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ans is 200 m.

as for shortest time the drift is

x =V(w)*t………V(w) is the velocity of water

120 m = V(w)*10 s

V(w)=12 m/s

also x=[ V(w)*d ]/V(m)…..V(m) is velocity of man.

therefore by solving d=10V(m)

now for shortest path

d={V(m) – V(w)}^1/2 * T

substuting the values we will get d=200m