Multiple choice

A boatman can row 60 km. downstream in 5 hr. If the speed of current 5 km/hr. then find in what time will he able to cover 8 km upstream? एक नाविक 5 घंटे में धारा की अनुकूल दिशा 60 किमी.जा सकता है। यदि धारा की चाल 5 किमी./घं तो कितने समय में वह धारा प्रतिकूल दिशा में 8 किमी. जायेगी?

  1. 6 hr./घंटे

  2. 4 hr./घंटे

  3. 8 hr./घंटे

  4. 5 hr./घंटे
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Downstream speed = 60/5 = 12 km/h. Speed of current = 5 km/h, so boat speed = 12 - 5 = 7 km/h. Upstream speed = 7 - 5 = 2 km/h. Time for 8 km upstream = 8/2 = 4 hours. Option A would need upstream speed of 1.33 km/h, option C would need 1 km/h, option D would need 1.6 km/h.

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