Correct Answer - Option 3 : 9 km/hr
Given:
Distance = 48 km
Time = 1 h
Upstream Time = 4 times the time
Formula Used:
Speed Upstream = Speed of boat in still water - Speed of current
Calculations:
Speed of boat in still water = 12 km/h
Speed against the current = 12/4 = 3 km/h
Let the speed of the current be x.
∴ According to the question
⇒ 12 - x = 3
⇒ x = 9km/h
The speed of the current is 9 km/h.