Ratio of time taken by a sailor to cover some distance upstream and downstream is 4 : 1. If speed of stream is 4.5 km/hr. Then find out speed of boat? 

The ratio of speed of boat in still water to speed of stream is 8 : 1. It takes 4 hours by boat to cover 54 km in downstream & 42 km in upstream. Find the downstream speed of boat.

A boat goes 30 km upstream and 44 km downstream in 10 hours. In 13 hours, it can go 40 km upstream and 55 km downstream. The speed of the boat in still water is. 

In a river the distance between two points is 80 km. A boat which rows 13 km/h in still water goes downstream from the first point to the second and returns upstream to starting point in 13 hrs., then find the speed of current. 

A man can swim at the rate of 3 km/hr. in still water. Then, if speed of the stream is 2 km/hr., then in what time he will cover a total distance of 5 km in with the stream and against the stream?

A boat travels 24 km upstream in 6 hours and 20 km downstream in 4 hours. Then the speed of boat in still water and the speed of current are respectively. 

Speed of a boat in still water is 6 km/hr and speed of the current is 2 km/hr. If boat takes four hours more in upstream than in the downstream to cover ‘D’ km, then find time take by boat to cover ‘D’ km in still water?

Two boats are traveling with speeds of 36 km/hr and 54 km/hr respectively towards each other. What is the distance (in meters) between the two boats one second before they collide?