Aptitude - Boats and Streams - Discussion
Discussion Forum : Boats and Streams - General Questions (Q.No. 14)
14.
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: Option
Explanation:
Let man's rate upstream be x kmph.
Then, his rate downstream = 2x kmph.
 (Speed in still water) : (Speed of stream) = |
 |
2x + x |  |
: | |
2x - x | |
| 2 | 2 |
| = | 3x | : | x |
| 2 | 2 |
= 3 : 1.
Discussion:
30 comments Page 3 of 3.
Omkar said:
1 decade ago
Let t1 = 2t2.
T1/T2 = 2/1.
But time is inversely proportional to speed. Speed = Distance/Time.
So s1/s2 = 1/2.
Speed of boat in still water = 1/2(2+1) = 3/2.
Speed of stream = 1/2(2-1) = 1/2.
3/2/1/2 = 3:1.
T1/T2 = 2/1.
But time is inversely proportional to speed. Speed = Distance/Time.
So s1/s2 = 1/2.
Speed of boat in still water = 1/2(2+1) = 3/2.
Speed of stream = 1/2(2-1) = 1/2.
3/2/1/2 = 3:1.
Zameer basha said:
1 decade ago
Dear @Srikanth.
In favour of stream means 'downstream' ==> (sd) = 1/1---taking it as a,
Against the stream means 'upstream' ==> (Su) = 1/2---taking it as b, now speed of stream will be positive value ((Sd)-(Su))/2.
Am I correct here reply.
In favour of stream means 'downstream' ==> (sd) = 1/1---taking it as a,
Against the stream means 'upstream' ==> (Su) = 1/2---taking it as b, now speed of stream will be positive value ((Sd)-(Su))/2.
Am I correct here reply.
Srikanth said:
1 decade ago
Let time taken to travel against the stream is 2,
Time taken to travel in favour of stream is 1,
As we know D=S*T,
As Distance is same (constant) so we can neglect it,
Speed downstream (Sd) = D/t =>1/2-----take it as a,
Speed upstream (Su) = D/t =>1-----take it as b,
We need to find ratio of the speed of the boat (in still water) to the stream is, i.e.
1/2(a+b):1/2(a-b).
==>1/2(1+1/2):1/2(1-1/2).
==>3:1.
Time taken to travel in favour of stream is 1,
As we know D=S*T,
As Distance is same (constant) so we can neglect it,
Speed downstream (Sd) = D/t =>1/2-----take it as a,
Speed upstream (Su) = D/t =>1-----take it as b,
We need to find ratio of the speed of the boat (in still water) to the stream is, i.e.
1/2(a+b):1/2(a-b).
==>1/2(1+1/2):1/2(1-1/2).
==>3:1.
R v said:
1 decade ago
Suppose speed upstream is x kmph.
Speed of current y kmph.
Time suppose is = t.
So (x+y)*t = (x-y)*2t because twice time taken from here we get.
y = x/3.
Now we need.
(x+y)/2:(x-y)/2.
Put value of why we get 2:1.
I think its right answer.
Speed of current y kmph.
Time suppose is = t.
So (x+y)*t = (x-y)*2t because twice time taken from here we get.
y = x/3.
Now we need.
(x+y)/2:(x-y)/2.
Put value of why we get 2:1.
I think its right answer.
Try said:
1 decade ago
Let the speed of man in still water = M.
Let the speed of stream = S.
Let speed of man in direction of stream = X.
Therefore,
M + S = X (Man in direction of stream).
M - S = X/2 (Man takes twice as much time it means his speed is 1/2*X).
-------------.
2M = 1.5*X.
=> M = 0.75*X.
=> S = 0.25*X.
=> M/S = 0.75/0.25 = 3/1.
Let the speed of stream = S.
Let speed of man in direction of stream = X.
Therefore,
M + S = X (Man in direction of stream).
M - S = X/2 (Man takes twice as much time it means his speed is 1/2*X).
-------------.
2M = 1.5*X.
=> M = 0.75*X.
=> S = 0.25*X.
=> M/S = 0.75/0.25 = 3/1.
Ravitheja said:
1 decade ago
Speed of still water is A = X.
Speed upstream is x/2.
Speed downstream B = 2xX = 2X+X = 3X.
B/A = 3/1 = 3:1.
Speed upstream is x/2.
Speed downstream B = 2xX = 2X+X = 3X.
B/A = 3/1 = 3:1.
Suhas said:
1 decade ago
Let speed of boat in downstream be 'x' kmph then speed of boat in upstream is 'x/2' kmph because time taken is twice hence.
A be the speed of boat and b be the speed of stream.
A+B = B.
A-B = X/2.
Hence A=3/4 and B=1/4.
Ratio is 3:1.
A be the speed of boat and b be the speed of stream.
A+B = B.
A-B = X/2.
Hence A=3/4 and B=1/4.
Ratio is 3:1.
Rajendra said:
1 decade ago
Can u explain how the below expression frames
2x+x/2
2x+x/2
Ani said:
1 decade ago
Why should it be greater than x but lessthan 2x?
Amit 7677 said:
1 decade ago
Speed should be greater than x but less than 2x.hence mean is taken of 2x and x i.e. 2x+x/2
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