Correct Answer - Option 2 : 3 hours
Given:
Speed of boat in still water = 16 km/hr
Speed of the stream = 5 km/hr
Boat to go 63 km downstream
Formula used:
Time = distance/speed
If the speed of a boat in still water is u km/hr and the speed of the stream is v km/hr, then,
Speed downstream = (u + v) km/hr
Calculation:
Speed downstream = (16 + 5) km/hr = 21 km/hr
Time taken to travel 63 km downstream = (63/21) hrs = 3 hrs
∴ Time taken to travel 63 km downstream is 3 hrs.