A boat which has a speed of 5 km/hr in still water crosses a river of width 3 km along the shortest possible path in t min. The river flows at the rate of 3 km/hr. Find the time taken t.
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Explanation:
let the velocity of the river be x. the velocity of the river will be in the horizontal direction
velocity of boat in still water is 5km/hr. As the width of the river is 1 km and time taken by the boat to cross the river along the shortest path is 15 min therefore the velocity of the boat is= 1*60/15= 4km/hr
according to the figure the velocity of the river is along AB . By applying triangle law of vector addition the value of AB comes to be 3km/hr
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