The ratio of the speed of a boat in still water to the speed of the stream is 5 : 1. If the downstream speed of the boat is 18 km/h, find the upstream speed (in km/hr).

Explanation

​ Information Given: Ratio of speed of boat in still water to stream = 5 : 1 Downstream speed = 18 km/h Concept/Formula Used: Downstream speed = Speed of boat in still water + Speed of stream Upstream speed = Speed of boat in still water − Speed of stream Explanation: Let speed of boat in still water = 5x Speed of stream = x Downstream speed = 5x + x = 6x Given, 6x = 18 x=3 Upstream speed = 5x − x = 4x = 4 × 3 = 12 km/h