একখানা নৌকা কোন নদীর স্রোতের সাথে সমকোণে যাত্রী করে যাত্রাবিন্দু হতে নদী বরাবর 1.5 কি.মি. দূরে অপর পাড়ে পৌছাল । নৌকার বেগ স্রোতের বেগের দ্বিগুণ হলে নদীর প্রস্থ কত?

The answer is correct because it considers the scenario where the speed of the boat is twice the speed of the river's current. In this case, we can use the concept of relative motion.

When the boat moves at an angle to the current, the actual path it takes includes both the distance moved downstream (due to the current) and the distance traveled across the river (perpendicular to the current).

Let's break this down:

    
• The boat travels straight across the river while also being carried downstream by the current.
    
• If the speed of the boat is 2 times the speed of the river, it effectively compensates for the flow of the river while crossing.
    
• If it takes a certain time to cross the river, the distance traveled downstream can be combined with the distance traveled across the river to find the river's width.

In calculations based on the problem, it can be determined that the width of the river is indeed 3 kilometers when you factor in these speeds and the setup provided.

Therefore, the correct answer of 3 কি মি reflects this relationship between the speeds and the distances involved in this problem.

AI-এর ব্যাখ্যায় ভুল থাকতে পারে।