If the speed of boat in still water is 9 km/hr & the speed of stream is 3 km/hr, the boat rows to a place which is 50 km far & returns through the same path. What would be the average speed of boat during the journey?
1
10 km/hr
2
5 km/hr
3
15 km/hr
4
8 km/hr
5
12 km/hr