Correct Answer - Option 3 : 5.5 km/hr
Given:
Length of upstream distance = 40 km
Time taken in upstream travel = 8 hr
Length of downstream distance = 36 km
TIme taken in downstream travel = 6 hr
Formula used:
Upstream speed = b - w
Downstream speed = b + w
b = speed of the boat in still water, w = speed of the stream
Speed = distance/time
Calculation:
According to the question:
b - w = 40/8 = 5 ----eq.1
b + w = 36/6 = 6 ----eq.2
Adding eq.1 and eq.2
2b = 11
⇒ b = 5.5
∴ Speed of the boat in still water = 5.5 kmph
