A boat with still water speed of a is traveling upstream where the streams speed is b. After covering certain distance s, the boat turns back and tries to come to the starting place. But the boat stops at 3/4th of the intended distance due to a technical fault. What is the ratio of the time taken for the return journey to that of the upstream journey.

a. 3(a - b)/4(a + b) b. 4(a - b)/3(a + b) c. 3(a + b)/4(a - b) d. 4/3

• speed of boat upstream = a - b
  speed of boat downstream = a + b
  
  For upstream journey, time taken = distance / speed = s / (a - b)
  
  During return journey, the boat had covered on 3/4th of s :
  
  Therefore for return journey, time taken = distance / speed = (3s/4)/(a+b)
  
  Ratio of time taken for return journey to the upstream journey = (3s/4)/(a+b)/ (s/(a - b)) = 3(a - b)/4(a + b)
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