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September 19, 2023
The subject matter of Boats and Streams Questions is quite essential as these questions are there in nearly all competitive exams from the topic. On this page we will discuss about Questions asked About the topic boats and streams.
where ,
s = speed of man. p2 = time taken to cover upstream p1 = time taken to cover downstream
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1. Alex can row a boat at 7 kmph downstream and 3 kmph upstream. Calculate her rowing speed in still water and the rate of the current?
5 Kmph and 2 kmph
7.5 kmph and 3 Kmph
6.4 kmph and 14 kmph
None of the above
Rowing speed of Alex in still water= (Rate upstream+ Rate Downstream)
= \frac{7 + 3}{2}= 5 kmph
And rate of the current= \frac{7 - 3}{2}= 2 kmph
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2. Sam’s Rowing speed is 10 kmph, but he takes double time in rowing the boat upstream in comparison to downstream. Calculate the rate of the stream?
2.18 kmph
3.33 kmph
1.56 kmph
4.36 kmph
Since it is mentioned that his speed downstream is twice that of the upstream.
So let Sam’s speed upstream be ‘a’ then his speed downstream= 2a
Therefore \frac{2a + a}{2}= 10 or a= 6.66 kmph
Hence his speed upstream= 6.66 kmph and
His speed downstream= 6.66*2= 13.33 kmph
Therefore the rate of the current= 3.33 kmph
3. What will be the speed of the boat if the river flows at a speed of 2 km/hr, and it takes 12 minutes to cover 4 km upstream?
21
16
22
30
Speed upstream = \frac{4}{\frac{12}{60}}= 20 km/hr Speed of the stream = 2 km/hr Speed of boat in still water = (20+2) = 22 km/hr
4. Calculate the speed of a motorboat in still water if current of the river flows at 2 kmph, and the boat takes 40 mins. To cover 10 km upstream and back again at the starting point.
19
30.13
26
None
Let the speed of the boat be ‘a’ (in still water)
Therefore speed downstream= a+2
And speed upstream= a-2
Time taken to cover 10 km back and forth= \frac{10}{a+2} + \frac{10}{a-2}= 40/60
= a2-30a-4= 0
Solving the above equation we get a = 30.13
5. Sam rows a boat at a speed of 6 kmph in still water. If the speed of the stream 2 kmph, in how much time will Sam take to cover 36 km downstream?
7
4.5
6.2
3
Speed of the boat with the stream= 6+2= 8 kmph
Therefore time taken by Sam to Cover 36 km= \frac{36}{8}= 4.5 hours
6. Tom takes 2 hours to sail a boat for 4 km against the stream and can cover 2 km distance in 20 minutes if he rows the boat along with the current of the river. Calculate the time taken to cover 10 km in stagnant water?
2.5
3.3
4.7
Speed Downstream= 2/20 * 60 = 6 kmph
Speed Upstream= 4/2= 2 kmph
Speed in stable water= \frac{6 + 2}{2}= 4 kmph
Hence time taken t cover 10 km= 10/4 = 2.5 hrs
7. Sam takes 12.5 minutes to cover 900 meters distance rowing the boat against the stream of the river and takes 7.5 minutes to row the same boat downstream. Calculate Sam’s speed of rowing the boat in still water?
5.76 kmph
4.75 kmph
2.65 kmph
3.22 kmph
Let the speed of the boat in still water be
Sam takes 12.5 minutes 750 seconds to cover 900 m upstream
Therefore speed upstream= 900/750 = 1.2 mps
As the time taken downstream 7.5 min or 450 sec
Therefore speed downstream = 900/450= 2 mps
Therefore speed in stable water= 1/2 * (1.2+2)= 1.6 mps
Or 1.6* (3600/1000) = 1.6 * 18/5= 5.76 kmph
8. The speed of a boat in still water is 4.5 kmph, and the rate of the river flow is 3 kmph. Calculate the total time taken by Agatha to cover a distance of 7.5 km to and fro in the same river?
6 hrs
5 hrs
4 hrs
5.5 hrs
Speed of the boat upstream= 4.5-3= 1.5 kmph
Speed of the boat downstream= 4.5+3= 7.5 kmph
Therefore total time taken=\frac{7.5}{1.5} + \frac{7.5}{7.5}= 5 + 1 = 6 hrs
9. Sam takes triple time to row a boat against the stream of the river than the time he takes to row with the stream to cover the same distance. What will be the ratio between the speed of the boat in still water to that of the flow?
3:2
2:1
3:1
4:3
Let Sam’s speed upstream be a kmph
Speed downstream= 3a kmph
Therefore the speed of the boat in still water: Speed of river stream
= \frac{3a +a}{2}:\frac{3a - a}{2}
= \frac{4a}{2}:\frac{2a}{2}Or 2: 1
10. Alex can row a boat in still water at a speed of 5 km/h. He rows the boat upstream for 2 hours and covers a distance of 10 km. Then, he rows downstream for 1.5 hours and covers a distance of 12 km. Calculate the speed of the stream.
2/7
1.5
1.4
4
Given: Speed of Boat in Still Water = 5 km/h Time taken upstream = 2 hours Distance upstream = 10 km Time taken downstream = 1.5 hours Distance downstream = 12 km
First, let's calculate the speed of the boat in the upstream and downstream directions:
Speed Upstream = Distance Upstream / Time Upstream Speed Upstream = 10 km / 2 hours Speed Upstream = 5 km/h
Speed Downstream = Distance Downstream / Time Downstream Speed Downstream = 12 km / 1.5 hours Speed Downstream = 8 km/h
Now, use the formula to calculate the speed of the stream:
Speed of Stream = (Speed Downstream - Speed Upstream) / 2 Speed of Stream = (8 km/h - 5 km/h) / 2 Speed of Stream = 3 km/h / 2 Speed of Stream = 1.5 km/h
So, the speed of the stream is 1.5 km/h.
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