Question

A man can row 7 1/2 kmph in still water.if in a river running at 1.5 km/hr an hour,it takes him 50 minutes to row to a place and back,how far off is the place?

Answer 1

Speed downstream =(7.5+1.5)km/hr=9 km/hr; 

Speed upstream=(7.5-1.5) kmph = 6kmph. 

Let the required distance be x km.then, 

x/9+x/6=50/60. 

2x+3x=(5/6*18) 

5x=15 

x=3. 

Hence,the required distance is 3 km.