Boats and Stream
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What is downstream and upstream ?
In water, the direction along the stream is called downstream. And, the direction against the stream is called upstream.
- If the speed of a boat in still water is u km/hr and the speed of the stream is v km/hr, then:
$$Speed\ of\ downstream = (u + v)\ km/hr$$
$$Speed\ of\ upstream = (u – v)\ km/hr$$ - If the speed downstream is a km/hr and the speed upstream is b km/hr, then:
$$Speed\ in\ still\ water = \frac{1}{2} (a + b)\ km/hr$$
$$Rate\ of\ stream = \frac{1}{2} (a – b)\ km/hr$$
1 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
2 A boat travels upstream from B to A and downstream from A to B in 3 hours. If the speed of the boat in still water is 9 km/h and the speed of the current is 3 km/h, find the distance between A and B in kilometres:
3 A man can row with a speed of 6 km/h in still water. What will be his speed with the stream, if the speed of stream is 2 km/h?
4 A man takes twice as long to row a distance against the stream as to row the same distance in favour of the stream. The ratio of the speed of the boat (in still water) and the stream is
5 A man can row 30 km upstream and 44 km downstream in 10 hours. Also, he can row 40 km upstream and 55 km downstream in 13 hours. Find the rate of the current and the speed of the man in still water:
6 8 Sekh can row a certain distance downstream in 12 h and can return the same distance in 18 h. If the stream flows at the rate of 6 km/h, then find the speed of Sekh in still water:
7 A boat takes 90 minutes less to travel 36 miles downstream than to travel the same distance upstream. If the speed of the boat in still water is 10 metre/hour, the speed of the stream is
8 Viraj can row downstream at 9 km/h and upstream at 5 km/h. Find the speed of Viraj in still water and speed of current:
