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August 11, 2023
Boats and streams is one of the most common topics in quantitative section of all the job entrance exams. On this page we will discuss how we can quickly solve Boats and streams problems.
Use the formula:
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Options:
A. 4 m/s
B. 5 m/s
C. 1 m/s
D. 3 m/s
Solution: Upstream speed = 900/300 = 3m/s
Downstream speed = 900/3 * 60 = 900/180 = 5m/s
Speed in still water = 1/2 (speed downstream + speed upstream)
= 1/2 (5 + 3)
= ½ (8)
= 4 m/s
Correct option: A
Question 2: The speed of a ship in still water in 20 km/hr and the rate of current is 15 km/hr. The distance travelled downstream in 4 minutes is:
A. 2.333 km/hr
B. 3.5 km/hr
C. 1.2 km/hr
D. 4 km/hr
Solution: Speed downstream = (20 + 15) km/h = 35 km/h
Distance covered in 4 minutes = 35 * 4/60 = 2.333 km/hr
Question 3: Find the ratio of the speed of the boat and the stream if Rakesh takes twice as long to row a distance in favour of the stream as to row the same distance against the stream.
A. 1:2
B. 3:1
C. 4:5
D. 1:1
Solution: Let the Rakesh’ upstream speed = x
Downstream speed = 2x
(Speed in still water): (Speed of stream) = (2x + x)/ 2: (2x – x)/2 = 3: 1
Correct option: B
A. 4 km/hr
B. 2 km/hr
C. 10 km/hr
D. 5 km/hr
Solution: Let the speed of stream = x
Speed of boat = 10 km/hr
Upstream speed = 6 km/hr
We know that, Upstream speed = speed of boat – speed of stream
6 = 10 – x
x = 10 – 6
x = 4 km/hr
Question 2: A man can row a boat upto 30 km down a river in 3 hours with the stream and can return back in 5 hours. What is the speed of the stream?
C. 6 km/hr
Solution: Speed Downstream= 30/3 = 10 km/hr
Speed Upstream = 30/5 = 6 km/hr
Speed of the stream = 1/2* (10 – 6) = 2 km/hr
Question 3: A man sail a boat to a place which is 24 km far. He reaches that place and comes back in 7 hours. He finds that he can sail a boat 3 km downstream in the same time as 2 km upstream. Find out the rate of the stream?
A. 1.43 km/hr
Solution: Suppose, He moves 3km downstream in x hours = 3/x km/hr
Speed Upstream = 2/x km/hr
24/(3/x) + 24/(2/x) = 7
8x + 12x = 7
x = 7/20
x = 0.35
So, Downstream Speed = 3/x = 3/ 0.35 = 8.57 km/hr
Upstream Speed = 2/0.35 = 5.71 km/hr
Rate of the stream = 1/2 (8.57 – 5.71) = 2.86/2 = 1.43 km/hr
A. 9 km/ hr
B. 5 km/ hr
C. 4 km/ hr
D. 3 km/ hr
Solution: Three-quarters of a kilometer = 750 meter
11(1/4) minutes = 45/4 = 675 seconds
7(1/2) minutes = 15/2 = 450 seconds
Upstream speed = 750/675 = 10/9 m/sec
Downstream speed = 750/450 = 5/3 m/sec
Speed in still water = ½ (10/9 + 5/3) = 25/18m/sec
To convert it into km/hr, multiply 25/18 by 18/5
= 5 km/hr
Question 2: A man’s speed with the current is 20 km/hr and the speed of the current is 5 km/hr. What is the man’s speed against the current?
A. 20 km/hr
B. 15 km/ hr
C. 5 km/ hr
D. 10 km/ hr
Solution: Man’s speed with the current = 20 km/hr
speed of the man + speed of the current = 20 km/hr
speed of the current is 5 km/hr
Hence, speed of the man = 20 – 5 = 15 km/hr
Man’s speed against the current = speed of the man – speed of the current
Man’s speed against the current = 15 – 5 = 10 km/hr
Correct option: D
Question 3:If a man sails a boat at the rate of 5 km/hr in still water. His upstream rate is 3 km/hr, then find the man’s speed along the current?
A. 7 km/hr
B. 5 km/hr
C. 8 km/hr
D. 10 km/hr
Solution: Let the speed along with the current = x km/hr
Therefore, (x+3)/2 = 5
x = 7km/hr
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