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 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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If a boat goes 7 km upstream in 42 minutes and the speed of the stream is 3 kmph, then the speed of the boat in still water is
Answer: B
Rate upstream = (7/42) × 60 kmh = 10 kmph.
Speed of stream = 3 kmph.
Let speed in sttil water is x km/hr
Then, speed upstream = (x —3) km/hr.
,p>x-3 = 10 or x = 13 kmph
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A man swims downstream 72 km and upstream 45 km taking 9 hours each time; what is the speed of the current?
Answer: B
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A boat takes half time in moving a certain distance downstream than upstream. What is the ratio between the rate in still water and rate of current?
Answer: B
Let the speed of the boat in still water be 4 km/hr and speed of the current be u km/hr.
Rate downstream = (u + v) km/hr.
Rate upstream = (u- v)km/hr
Let the distance covered in each case be x km.
Then 2x/(u + v) = x / (u - v)
=> 2 (u - v) = ( u + v)
=> u =3v
=> u/v =3/1
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3 towns P, Q and R are located at the bank of a stream. Distance of Q from P and R is same. Jeet rows from P to Q and Q to P in total 10 hours. Jeet also requires 4 hours to row from P to R. If the stream flows at a consistent rate what will be the ratio of Jeet’s speed in still water and speed of stream?
Answer: B
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What is speed of Ram in still water and speed of river, if Ram covers 20 km in 1 hour swimming downstream and covers the same distance in 2 h swimming upstream?
Answer: D
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Simran takes twice as long to swim up as to swim down the river and has a speed of 12 km/hr in still water. What is river’s speed?
Answer: D
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If a boat is rowed downstream for 50 km in 5 hours and upstream for 24 km in 6 hours, what is the speed of the boat and the river?
Answer: A
If x: speed of boats man in still water
y: speed of the river
Downstream speed (Ds) = x + y
Upstream speed (Us) = x – y
x = (Ds + Us) / 2
y = (Ds – Us) / 2
In the above problem Ds = 10 ; Us = 4
x = (10 + 4) / 2 = 14/2 = 7 km/hr
y = (10 - 4)/2 = 6/2 = 3 km/hr
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A man can row at 5 km/hr in still water, if the river is running at 1 km/hr it takes him 75 minutes to row to a place and back. How far is the place?
Answer: B
Speed downstream = (5+1)km/hr = 6 km/hr
Speed upstream = (5-1)km/hr = 4 km/hr
Let the required distance be x km.
Then x/6 + x/4 = 75/60 = 5/4 => (2x + 3x) =15 => x =3.
Required distance = 3 km
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