A boat running downstream covers a distance of 50 km in 2(1/2) hrs and the same distance upstream in 10 hrs. What is the speed of the boat in still water?

Let the speed of boat in still water be x km/hr Speed of the stream = y km/hr Now, speed downstream (u) = (x + y) km/hr, and Speed upstream (v) = (x - y) km/hr According to question, Speed downstream = distance/time (x + y) = (50 × 2)/5 (x + y) = 20……………(i) Speed upstream = distance/time (x - y) = 50/10 (x - y) = 5…………………..(ii) Now, speed of boat in still water = (u + v)/2 km/hr ∴ Speed of boat in still water = (20 + 5)/2 km/hr = 25/2 km/hr = 12.5 km/hr

- A motorboat in still water travels at a speed of 36 km/hr. It goes 64 km upstream in 2 hours. The time taken by it to cover the same distance down the stream will be :
- A boy can swim in water with a speed of 10 km/hr in still water. If the speed of the stream is 4 km/hr, what will be the time taken by the boy to cover 70 km downstream?
- A boat takes 7 hours to cover 259 km upstream and 9 hours to cover 477 km downstream. Find the time taken by the boat to cover 645 km upstream and 660 km downstream if speed of boat in still water is increased by 4 km/h and speed of stream is decreased by 2 km/h.
- A boat running downstream covers a distance of 48 km in 3 hrs and covering the same distance upstream in 12 hrs. What is the speed of a boat in still water?
- A boat takes 7 hours to cover 245 km upstream and 9 hours to cover 477 km downstream. Find the time taken by the boat to cover 410 km upstream and 495 km downstream if speed of boat in still water is increased by 4 km/h and speed of stream is decreased by 2 km/h.
- A man’s speed with the current is 50 km/hr and the speed of the current is 5 km/hr. The man’s speed against the current is:
- A boy can swim a certain distance downstream in 3 hours and return in 7 hours. If the rate of stream is 4 kmph then what is the speed of boy in still water?
- Speed of a boat in still water is 15 kmph and speed of stream is 12 kmph. A man rows to a place at a distance of 81 km and come back to starting point. The total time taken by him is:
- A man swims downstream 60 km and upstream 36 km, taking 12 hr each time. Find the man’s rate in still water?
- Speed of boat is 30 km/hr. Speed of the stream is 20% less than speed of boat. Then find time taken by boat to go 108 km downstream?

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