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The question of minimum time and minimum distance in crossing a river.

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


1 Comment

  1. 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

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