Boats and Streams

A man's speed with the current is 15 km/hr and the speed of the current is 2.5 km/hr. The man's speed against the current is:

In one hour, a boat goes 11 km/hr along the stream and 5 km/hr against the stream. The speed of the boat in still water (in km/hr) is:

A man takes twice as long to row up the stream as to row down the stream. The ratio of the speed of the boat (in still water) to the stream is:

A man can row at 5 kmph in still water. If the velocity of current is 1 kmph and it takes him 1 hour to row to a place and come back, how far is the place ? 

A boat covers a certain distance downstream in 1 hour, while it comes back upstream in 1 1/2 hours. If the speed of the stream be 3 kmph, what is the speed of the boat in still water?  

A motorboat, whose speed in 15 km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes. The speed of the stream (in km/hr) is: 

Speed of a boat in still water is 9 kmph and the speed of the stream is 1.5 kmph. A man rows to a place at a distance of 105 km and comes back to the starting point. The total time taken by him is: 

A man can row 6 km/ hr in still water. If it takes him twice as long to row up, as to row down the river, then the rate of current in the stream is:

A boat goes 24 km upstream and 28 km downstream in 6 hrs. If it goes 30 km upstream and 21 km downstream in 6 hrs and 30 mins, find the speed of the stream. 

A boat takes 90 minutes less to travel 24 km downstream than to travel the same distance upstream. If the speed of the boat in still water is 12 km/h, the speed of the stream is: