A runs four times as fast as B. If A gives B a start of 90 meters, how far must the goal on the race course be so that A and B reach it at the same time ?

Ravi row to a place 45km distant and back in 20 hours. He finds that he can row 12km with stream in the same time as 4km against the stream ,then the speed of the stream is:

A man rows 15 km upstream in 5 hours and 25 km downstream in 5 hours each time, then the speed of the stream is

Let the speed of a boat in still water be $u$ km/hr and the speed of the water current in a river be $v$ km/hr. If a man rows distance $D$ down stream and same distance upstream, then average speed of total journey is

The speed of a boat in still water is 15 km/hr. It takes twice as long to go upstream to a point as to return downstream to the starting point. The speed of the stream is:

A swimmer whose speed in still water is 6 km/hr, swims between two points in a river and returns to the starting point. He took 20 minutes more to cover the distance upstream than downstream. If the speed of the stream is 3 km/hr, then the distance between the two points is:

The ratio of the speed of a motorboat and that of the current of water is 14 : 8. The boat goes a certain distance along with the current in 3 hours 12 minutes. How much time does it take to come back?