The speed of a boat in still water is thrice the speed of the stream. If the boat takes 15.5 sec to go to a certain place downstream, then find the additional time required to cover the same distance travelling upstream.

15.5 sec

We know that,

Total speed downstream = Speed of boat + Speed of stream

Total speed upstream = Speed of boat – Speed of stream

We have,

The speed of the boat is thrice the speed of the stream.

Time taken to go to a certain place downstream = 15.5 sec

Now according to the question,

Let the distance be y.

Let the speed of the stream be x.

So, the Speed of the boat will be 3x.

Total Speed in downstream = 3x + x = 4x

Using the speed formula, we get

= y = 15.5 × 4x = 62x

Total Speed in upstream = 3x – x = 2x

= 62x = t × 2x

= t = 62x/2x = 31 sec

Additional time required to travel upstream = 31 – 15.5 = 15.5 sec