Multiple choice

A boat goes 96 km in upstream and return back 32 km in downstream and takes 14 hours to complete the journey. If the speed of boat in upstream is 8 km/hr. Then find the ratio of speed of boat in still water and speed of stream. एक नाव धारा के विरूद्ध 96 किमी जाती है तथा धारा के साथ वापस 32 किमी आती है, इस प्रकार कुल यात्रा में 14 घण्टे लगते हैं । यदि धारा के विरूद्ध नाव की चाल 8 किमी/घंटा है तो शान्त जल में नाव की चाल तथा धारा की चाल का अनुपात ज्ञात कीजिये ।

  1. 3 : 1

  2. 2 : 1

  3. 4 : 1

  4. 5 : 3

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A Correct answer
Explanation

Upstream speed = 8 km/hr, so 96 km upstream takes 96/8 = 12 hours. Total time is 14 hours, leaving 2 hours for downstream. Downstream speed = 32/2 = 16 km/hr. Let boat speed = b and stream speed = s. Then b - s = 8 and b + s = 16. Solving: 2b = 24, so b = 12 km/hr and s = 4 km/hr. The ratio b:s = 12:4 = 3:1.