Speed of river is 6 km/hr. Speed of a motorboat in still water is 30km/hr. How much distance can it cover downstream in 24minutes?
Answer: D
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A boat can move upstream at 25 kmph and downstream at 35 kmph, then the speed of the current is?
Answer: A
US = 25
DS = 35
M = (35 - 25)/2 = 5
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A boat with speed 15 km/hr in standing water goes 30 km downstream and returns in a total of 4.5 hours. What is the speed of current?
Answer: C
Speed of the boat in still water: 15 km/hr
Speed of boat downstream: (15+x)km/hr where x is speed of the current.
The boat travels 30 km downstream and then 30 km upstream and takes 9/2 hours.
Total time= Time taken to travel downstream + Time taken to travel upstream
=> 4/5= (30/(15+x))+(30/(15-x))
=>x= 5
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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:
Answer: B
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A man can row 7 ½ kms on hour in still water and he finds that it takes hi twice as long to row down the river. The rate of stream is
Answer: B
Let the rate of the stream be x km/hr.
Then Speed downstream = (15/2 + x)km/hr.
Speed upstream = (15/2 -x)km/hr
(15/2 + x) = 2 (15/2 - x)
=> 3x =15/2
=> x = 15/6 = 5/2 = 2.5
Therefore, Rate of stream = 2.5 km/hr
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A man can row 9 1/3 km/hr in still water and he finds that is thrice as much time to row u p than as to row down the same distance in river. The speed of the current is:
Answer: D
Let Speed upstream = x km/hr
Speed downstream = 3x km/hr
Speed in still water = ½ (x+3x) km/hr = 2x km/hr
Speed of current = ½ (3x-x) km/hr = x km/hr
2x = 28/3 or x = 14/3 = 4 2/3 km/hr
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A steamer goes downstream from one port to another in 4 hours, it covers the same distance upstream in 5 hours. If the speed of the stream is 2km/hr,the distance between the two parts is?
Answer: D
Let the distance between the two parts be x km.
Then speed downstream = x/4 km/hr.
Speed Upstream = x/5 km/hr
Speed of the stream = ½ (x/4 –x/5)
Therefore, ½(x/4 –x/5) = 2. => x/4 –x/5 = 4 => x = 80.
Hence, the distance between the two ports is 80km.
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Ajay takes 4 hours more while swimming upstream than downstream. His speed in still water is 10 km/hr. The speed of stream is 2 km/hr. What is the distance?
Answer: A
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A boats man can row in still water at speed of 7 km/hr. It takes 6 hours more to travel the same distance in upstream than in downstream if the speed of the river is 3 km/hr. what is the distance between the two destinations?
Answer: B
x = 7 km/hr ; y = 3 km/hr
Ds = 10 km/hr ; Us = 4 km/hr
Distance (d) is same. Therefore, if time taken for downstream is t hours, the time for upstream is (t + 6) hours.
10*t = 4*(t + 6)
6t = 24 ; t = 4 hours
d = 10*4 = 40 km
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The speed at which a man can row a boat in still water is 15 kmph. If he rows downstream, where the speed of current is 3 kmph, what time will he take to cover 60 metres?
Answer: D
Speed of the boat downstream = 15 + 3 = 18 kmph
= 18 * 5/18 = 5 m/s
Hence time taken to cover 60 m = 60/5 = 12 seconds.
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