Multiple choice

A boat rows downstream covers a distance of 20 km. in 2 hrs while it covers the same distance upstream in 250% of the downstream time. Then speed of the boat in still water is- एक नाव धारा के अनुकूल 20 किमी की दूरी 2 घंटे में तय करती है जबकि यह समान दूरी ऊर्ध्वप्रवाह में धारा के अनुकूल लगे समय के 250% समय में तय करती है तो नाव की स्थिर जल में चाल है-

  1. 7 kmph/किमी/घंटा

  2. 8 kmph/किमी/घंटा

  3. 9 kmph/किमी/घंटा

  4. 10 kmph/किमी/घंटा
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A Correct answer
Explanation

Downstream speed = 20/2 = 10 kmph. Upstream time = 250% of 2 hrs = 5 hrs, so upstream speed = 20/5 = 4 kmph. Boat speed in still water = (downstream + upstream)/2 = (10+4)/2 = 7 kmph. Stream speed = (downstream - upstream)/2 = 3 kmph.

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