Boats and Streams

A boatman goes 2 km upstream in 1 hour and goes 1 km downstream in 10 minutes. How long will it take to go 5 km 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: 

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 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 person can row with the stream at 8 km/hr and against the stream at 6 km/hr. The speed of the current is:

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:

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:

The speed of a boat in still water is 15 km/hr and the rate of current is 3 km/hr. The distance travelled downstream in 12 minutes is:

A man can row at 5 km/hr in still water. If the river is running at 1 km/hr, it takes him 75 min to row to a place and come back. How far is the place ? 

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: