Answer:
The speed of the flow of water in the river is 4 m/s.
Explanation:
Given that,
Speed of man = 5 m/s
If this man swims crosses a specific river his speed is 3 m/s.
If he takes the minimum time to cross the river
Let the speed of flow of water be 
We need to calculate the speed of the flow of water in the river
Using formula for velocity


Where,
= velocity of swimmer
= relative velocity
= velocity of river
Put the value into the formula



Hence, The speed of the flow of water in the river is 4 m/s.