The downstream speed of a boat is 18 km/h, and the speed of the stream is 3 km/h. Find the time taken (in hours) by the boat to cover a distance of 30 km upstream.

Correct option is C

Information Given in the Question:
Downstream speed = 18 km/h
Speed of the stream = 3 km/h
Distance to cover upstream = 30 km
Concept/Formula Used in the Question:
Speed of boat in still water = (Downstream speed - Stream speed)
Upstream speed = (Speed of boat in still water - Stream speed)
Time = Distance / Speed
Detailed Explanation:
Speed of boat in still water = 18 - 3 = 15 km/h
Upstream speed = 15 - 3 = 12 km/h
Time taken = Distance / Upstream speed
=30/12 = 2.5 hours