Multiple choice

A boat takes double of the time taken by it to go downstream while coming in upstream. If speed of the current is 3 km/hr. Find how much percent more the speed of the boat is ? एक नाव धारा के ऊर्ध्वप्रवाह जाने में अनुप्रवाह जाने में लगे समय का दोगुना लेती है | यदि धारा की चाल 3 किमी./घंटा है | ज्ञात कीजिये कि नाव की चाल, धारा की चाल से कितने प्रतिशत अधिक है ?

  1. 200%

  2. 300%

  3. 100%

  4. 0%
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A Correct answer
Explanation

Let boat speed = b, current speed = c = 3 km/hr. Downstream speed = b + c, upstream speed = b - c. Time upstream = 2 × Time downstream, so distance/(b-c) = 2 × distance/(b+c). This gives b + c = 2(b - c), so b = 3c = 9 km/hr. Percentage more = (9-3)/3 × 100 = 200%.

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