The ratio of time taken by a boat to cover a distance in downstream to that of in upstream is 2 : 3. If the boat covers 108 km in downstream in ‘d’ hours and 120 km in upstream in d+4 hours, then find upstream speed (in km/hr) of the boat?

The time taken by a boat to go 18 km downstream is equal to the time taken by it to go 10.8 km upstream. The speed of the boat in still water is 8 km/h. How much time (in hours) will the boat take to go 45 km upstream?

The time taken by a boat to travel 75 km upstream is equal to 1$$\frac 23$$of  the time it takes to travel 60 km downstream. The speed of the boat in still water is 28 km/h. How much time (in hours) will the boat take to travel 51.2 km downstream?

The downstream speed of a boat is 18 km/h, and the speed of the stream is 3 km/h. Find the time taken (in hours) by the boat to cover a distance of 30 km upstream.

A boat can go 15 km upstream and 21 km downstream in 2 hours. If the speed of the stream is 3 km/h, then the time taken (in hours) by the boat to go 21 km upstream and 15 km downstream is :