Time taken by Naimish to travel a distance upstream is 7 times of the time which he takes to travel the same distance downstream. If the distance between the destinations is 60 Km which he can travel in 5 hours in still water, then find the rate of the stream.

Let upstream time = 7t and downstream time = t. Distance = 60 km each way. Upstream: 60/(b - s) = 7t. Downstream: 60/(b + s) = t. This gives (b + s)/(b - s) = 7. Cross-multiplying: b + s = 7b - 7s, so 8s = 6b, giving s = 3b/4. Boat speed in still water: 60/5 = 12 km/hr (covers 60 km in 5 hours). So s = 3 × 12 / 4 = 9 km/hr.