Speed of boat to that of speed of stream is 7 : 2. If the boat covers certain distance downstream in 1 hour then find the time(in minutes) taken by boat to cover the same distance in upstream.

Given:

The speed of the boat to the speed of the stream is in the ratio 7 : 2.

The boat covers a certain distance downstream in 1 hour.

Let the speed of the boat be 7x and the speed of the stream be 2x.

Calculation:

The effective speed of the boat downstream is the sum of the boat's speed and the stream's speed:

Speed downstream = 7x + 2x = 9x

It is given that the boat covers a certain distance downstream in 1 hour. So, the distance covered downstream is:

Distance = Speed × Time = 9x × 1 = 9x

Now, to cover the same distance upstream, the effective speed of the boat is the difference between the boat's speed and the stream's speed:

Speed upstream = 7x - 2x = 5x

The time taken to cover the same distance upstream is:

Time = Distance / Speed = 9x / 5x = 9 / 5 hours

Converting the time to minutes (since 1 hour = 60 minutes):

Time in minutes = (9 / 5) × 60 = 108 minutes

∴ The time taken by the boat to cover the same distance upstream is 108 minutes.