A man can swim at the rate of 5kmh−1 in still water. A 1−km wide river flows at the rate of 3 km h−1. The man wishes to swim across the river directly opposite to the starting point. How much time will he take to cross the river
Question
A man can swim at the rate of 5kmh−1 in still water. A 1−km wide river flows at the rate of 3 km h−1. The man wishes to swim across the river directly opposite to the starting point. How much time will he take to cross the river
Solution
The man's speed in still water is 5 km/h and the river's speed is 3 km/h. When the man swims against the current, his effective speed is the difference between his swimming speed and the river's speed.
So, his effective speed = (man's speed) - (river's speed) = 5 km/h - 3 km/h = 2 km/h.
The width of the river is 1 km.
The time taken to cross the river is given by the formula:
Time = Distance / Speed
So, the time taken by the man to cross the river = Distance / Effective Speed = 1 km / 2 km/h = 0.5 hours.
Therefore, the man will take 0.5 hours (or 30 minutes) to cross the river.
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