Correct Answer - Option 4 : 22 hours
Given:
Speed of boat in still water = 11 kmph
Speed of stream = 2 kmph
Distance = 117 km
Formula used:
Downstream speed = Speed of boat + Speed of stream
Upstream speed = Speed of boat – Speed of stream
Speed = Distance/Time
Calculations:
Let the downstream speed and upstream speed be d and u respectively
Downstream speed
⇒ d = 11 + 2 = 13 kmph
Upstream speed
⇒ u = 11 – 2 = 9 kmph
Time taken in going upstream and downstream
⇒ (117/9) + (117/13)
⇒ 13 + 9
⇒ 22 hours
∴ The man will go upstream and downstream in 22 hours