Multiple choice

The speed of current is 4 kmph. A boat takes the same time in going 20 km downstream while as it goes 12 km upstream. Find the speed of the boat. धारा की चाल 4 किमी./घंटा है | एक नाव 20 किमी. धारा के अनुप्रवाह जाने में समान समय लेती है जितना कि 12 किमी. ऊर्ध्वप्रवाह जाने में लेती है | नाव की चाल ज्ञात कीजिये |

  1. 12 kmph (किमी./घंटा)

  2. 15 kmph (किमी./घंटा)

  3. 16 kmph (किमी./घंटा)

  4. 10 kmph (किमी./घंटा)
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let boat speed = b. Downstream speed = b+4, upstream = b-4. Times are equal: 20/(b+4) = 12/(b-4). Cross-multiplying: 20b - 80 = 12b + 48, giving 8b = 128, so b = 16 kmph. Option B (15) would not satisfy the time equality condition.

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