Speed of the motorboat in still water is 45 Km/hr. If the motorboat travels 80 km along the stream in 1 hour 20 min, then the time taken by it to cover the same distance against the stream will be

First, let's convert the time of 1 hour 20 minutes to hours. 20 minutes is 1/3 of an hour, so the time is 1.33 hours.

The speed of the motorboat along the stream is the distance divided by the time, which is 80 km / 1.33 hours = 60 km/hr.

The speed of the stream is the difference between the speed of the motorboat along the stream and the speed of the motorboat in still water, which is 60 km/hr - 45 km/hr = 15 km/hr.

The speed of the motorboat against the stream is the difference between the speed of the motorboat in still water and the speed of the stream, which is 45 km/hr - 15 km/hr = 30 km/hr.

The time taken by the motorboat to cover the same distance against the stream is the distance divided by the speed, which is 80 km / 30 km/hr = 2.67 hours, or approximately 2 hours and 40 minutes.

First, let's understand the problem. The speed of the motorboat in still water is 45 km/hr. When the boat is moving along the stream, the speed of the stream aids its motion, making it faster. When it's moving against the stream, the speed of the stream hinders its motion, making it slower.

Step 1: Calculate the speed of the stream The boat covers 80 km along the stream in 1 hour 20 min, which is 1.33 hours (80 minutes / 60). So, the speed of the boat along the stream is distance/time = 80 km / 1.33 hr = 60 km/hr.

Since the speed of the boat in still water is 45 km/hr, the speed of the stream is the difference between the speed of the boat along the stream and the speed in still water. So, speed of stream = 60 km/hr - 45 km/hr = 15 km/hr.

Step 2: Calculate the time taken to cover the same distance against the stream When the boat is moving against the stream, its effective speed is the difference between its speed in still water and the speed of the stream. So, effective speed = 45 km/hr - 15 km/hr = 30 km/hr.

The time taken to cover a certain distance is the distance divided by the speed. So, the time taken to cover 80 km against the stream is distance/speed = 80 km / 30 km/hr = 2.67 hours, which is approximately 2 hours and 40 minutes.