The speed of a boat in still water is 10 km/hr. It covers (upstream) a distance of 45 km in 6 hour. The speed (in km/hr) of the stream is?

2.5

Upstream speed =  \(\frac{45}{6}\) = 7\(\frac{1}{2}\) km/hr = Spped of boat - speed of current

Speed of boat - speed of current = 7\(\frac{1}{2}\) km/hr

 10 km/hr  - speed of current = 7\(\frac{1}{2}\)  km/hr

                   speed of current = 2\(\frac{1}{2}\)  km/hr