A boat can travel with a speed of $13$ km/hr in still water. If the speed of the stream is $4$ km/hr, find the time taken by the boat to go $68$ km downstream.
Can you Explain the Difference between speed and Relative Speed? Share some basic concepts what are the things I have to Remember when doing Boats and Streams Problems.
The stream's speed works against the boat when it is traveling upstream, and with the boat if it is going downstream as in your situation.
The boats speed is as you said 13 km/h but its relative speed is its speed plus the rivers speed,
13 + 4 = 17 km/h .
So the boat travels at 17km/h, now you can use speed = distance/time to calculate the time taken to travel the 68km.