If a sailer sails 12 km distance within 5 hours against the flow of a river. If he sails 22 km distance in same time along the flow of the river. Then velocity of the river is _______

A man swims downstream distance of 15 km in 1 hour. If the speed of the current is 5 km/ hr, the time taken by the man to swim the same distance upstream is : 

A man can row 30 km downstream and return in a total of 8 hours. If the speed of the boat in still water is four times the speed of the current, then the speed of the current is: 

Ratio between speed of boat in still water to speed of stream is 7 : 2. If 126 km is travelled downstream in 3.5 hours then find the difference between speed of boat in still water to speed of stream(in kmph)?

The speed of the current is 5 km / hour. A motorboat goes 10 km upstream and back again to the starting point in 50 minutes. The speed (in km / hour) of the motorboat in still water is: 

A boat running downstreams covers a distance of 30 kms in 2 hours. While coming back the boat takes 6 hours to cover the same distance. If the speed  of the current is half that of the boat, what is the speed of that boat in kmph?