Multiple choice

A boat goes 50 km downstream and comes back in a total time of 7 hours 30 minutes. Find the time taken by the boat to cover a distance of 60 km downstream if it's speed in still water is 15 kmph. एक नाव धारा के अनुकूल 50 किमी. जाती है और वापस कुल 7 घंटे 30 मिनट समय में वापस आती है। 60 किमी. अनुप्रवाह जाने में नाव द्वारा लिया गया समय ज्ञात कीजिए यदि इसकी स्थिर जल में चाल 15 किमी/घंटा है।

  1. 3 hours/घंटे

  2. 4 hours/घंटे

  3. 5 hours/घंटे

  4. 6 hours/घंटे
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A Correct answer
Explanation

Let v=15 kmph (still water), u=stream speed. Downstream speed = 15+u, upstream = 15-u. Total time: 50/(15+u) + 50/(15-u) = 7.5 hours. Solving gives u=5 kmph. Time for 60 km downstream = 60/(15+5) = 60/20 = 3 hours. Options B, C, D are incorrect - they don't satisfy the given conditions.

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