Aptitude - Boats and Streams - Discussion
Discussion Forum : Boats and Streams - General Questions (Q.No. 10)
10.
A boat covers a certain distance downstream in 1 hour, while it comes back in 1
hours. If the speed of the stream be 3 kmph, what is the speed of the boat in still water?
hours. If the speed of the stream be 3 kmph, what is the speed of the boat in still water?
Answer: Option
Explanation:
Let the speed of the boat in still water be x kmph. Then,
Speed downstream = (x + 3) kmph,
Speed upstream = (x - 3) kmph.
 (x + 3) x 1 = (x - 3) x |
3 |
| 2 |
2x + 6 = 3x - 9
x = 15 kmph.
Discussion:
20 comments Page 1 of 2.
SAnil said:
1 decade ago
Why we not take ?
3/x+3 + 3/x-3 = 5/2 ( total hrs = 1 hrs + 1 1/2 hrs)
3/x+3 + 3/x-3 = 5/2 ( total hrs = 1 hrs + 1 1/2 hrs)
(3)
Priya said:
1 year ago
The ratio between time in downstream to upstream is 1:3/2 = 2:3, then the ratio between speed is 2 : 3(directly proportional).
The difference between the ratio is 1 and is given as 3.
The speed of still water is x+y that is (2+3)×3 = 15.
The difference between the ratio is 1 and is given as 3.
The speed of still water is x+y that is (2+3)×3 = 15.
(1)
VYSHU said:
3 years ago
@All.
By checking the options we can find the answer.
Time has already been given in the question. And these options are the speed of the boat in still water.
And you know the rate of current as well. Just check which option gives you the same distance upstream as well as downstream (D=S*T).
By checking the options we can find the answer.
Time has already been given in the question. And these options are the speed of the boat in still water.
And you know the rate of current as well. Just check which option gives you the same distance upstream as well as downstream (D=S*T).
(1)
Ketan said:
6 years ago
If Time=Distance/Speed.
Speed=Distance*Time.
According to condition distance of D.S and U.S is same.
D.S=U.S.
(x+3)*1=(x-3)*3/2 {Remember S=D*T.}.
{i.e D.S and U.S distance which is x+3 and x-3 respectively} and {D.S and U.S time which is 1 and 1*1/2=3/2 respectively}
2x+6=3x-9 (Multiply both equations by 2 to get rid of denominator 2 and solve).
6+9=3x-2x.
x=15.
Speed=Distance*Time.
According to condition distance of D.S and U.S is same.
D.S=U.S.
(x+3)*1=(x-3)*3/2 {Remember S=D*T.}.
{i.e D.S and U.S distance which is x+3 and x-3 respectively} and {D.S and U.S time which is 1 and 1*1/2=3/2 respectively}
2x+6=3x-9 (Multiply both equations by 2 to get rid of denominator 2 and solve).
6+9=3x-2x.
x=15.
(1)
Kousalya said:
7 years ago
Yes, you are right. @Syed.
But we find only the distance. But the question asked is the speed of the boat in still water.
Can anyone explain this?
But we find only the distance. But the question asked is the speed of the boat in still water.
Can anyone explain this?
(1)
Natraj said:
7 years ago
The speed of the boat in still water formula is 1/2(a-b) right then why there is no usage of formula here.
(1)
Swapnagolla said:
8 years ago
Why we taken x-3 why can't 3-x?
Please explain me.
Please explain me.
(1)
Nikul Rana said:
1 decade ago
Suppose we assuming the distance D;
So the speed downstream = X+Y = D/1;
Therefor X+Y = D;.....1.
And the speed upstream = X-Y = 2D/3;
(3X- 3Y)/3 = D......2.
If we compare both equations and take Y = 3 kmph as given;
We will get X = 15 kmph which is the speed of still water.
So the speed downstream = X+Y = D/1;
Therefor X+Y = D;.....1.
And the speed upstream = X-Y = 2D/3;
(3X- 3Y)/3 = D......2.
If we compare both equations and take Y = 3 kmph as given;
We will get X = 15 kmph which is the speed of still water.
Suraj dev said:
9 years ago
It has a simple formula. A man rows certain distance downstream in x hrs and returns the same distance in y hrs . when to stream flows at a rate of a km/hr then,
Speed of boat or man in still water = a(x + y)/(y - x),
That is speed of boat in still water = 3(1 + 1.5)/(1.5 - 1) = 15 km/hr.
You can also find the speed of stream when the boat is traveling with b km/hr = b(y - x)/(x + y).
Speed of boat or man in still water = a(x + y)/(y - x),
That is speed of boat in still water = 3(1 + 1.5)/(1.5 - 1) = 15 km/hr.
You can also find the speed of stream when the boat is traveling with b km/hr = b(y - x)/(x + y).
Subha.R said:
9 years ago
Is there any shortcut way?
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