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 2 of 3.
Manoj said:
7 years ago
The distance is same so,
D/t = x.
where x is the speed of the boat in downstream.
D/t = 2x in upstream case.
D/t = x.
where x is the speed of the boat in downstream.
D/t = 2x in upstream case.
Sajith said:
8 years ago
Let d= distance and x = time.
Speed in still water = 1/2(speed in down stream + speed in up stream).
= 1/2 (d/x + d/2x) => eqn 1.
Rate of stream = 1/2( speed in down stream - speed in up stream).
= 1/2(d/x - d/2x) => eqn 2;
We need eqn 1 : eqn 2.
On simplification, we will get 3:1.
Speed in still water = 1/2(speed in down stream + speed in up stream).
= 1/2 (d/x + d/2x) => eqn 1.
Rate of stream = 1/2( speed in down stream - speed in up stream).
= 1/2(d/x - d/2x) => eqn 2;
We need eqn 1 : eqn 2.
On simplification, we will get 3:1.
Vishi said:
8 years ago
Boat speed(B) +stream speed (S).
B+S = x
B-S = 2x
BY adding
2B = 3x
B= 1.5 x
By substracting
2S = -x
S= -.5 on neglecting - sign .5x
Ration becomes .5 : 1.5
Which is 1:3 also
Stream speed : boat speed.
B+S = x
B-S = 2x
BY adding
2B = 3x
B= 1.5 x
By substracting
2S = -x
S= -.5 on neglecting - sign .5x
Ration becomes .5 : 1.5
Which is 1:3 also
Stream speed : boat speed.
Mohit said:
8 years ago
Downstream distance(x) : upstream distance(y)= 2:1.
Boat speed(u) : stream speed(v)= x+y : x-y.
= 3 : 1 --> answer.
Boat speed(u) : stream speed(v)= x+y : x-y.
= 3 : 1 --> answer.
Einstein said:
8 years ago
How you relate the speed of the man with speed of the boat? Explain it.
Pranay pal said:
9 years ago
Let,
Boat speed=b
Speed of water= w
Upstream speed =b"w= x kmph---> eqn a.
Downstream speed= b+w= 2x kmph
b+w= 2x kmph
b+w= 2(b"w) kmph
3w= b kmph
Putting value of w in equation a.
M/x = 3/2
Answer would be 3:2.
Boat speed=b
Speed of water= w
Upstream speed =b"w= x kmph---> eqn a.
Downstream speed= b+w= 2x kmph
b+w= 2x kmph
b+w= 2(b"w) kmph
3w= b kmph
Putting value of w in equation a.
M/x = 3/2
Answer would be 3:2.
Ecoist said:
9 years ago
Let's call Speed of Boat as B and Speed of Stream as S.
Distance = Time x Velocity.
Let's call Time with T.
Distance with Favour is (B + S) x T.
Distance against the stream is (B - S) x T.
Since the distance is twice if the stream is in favour
So, (B + S) x T = (B - S) x T x 2,
B + S = 2B - 2S,
B = 3S.
So, the ratio is 3 : 1.
Distance = Time x Velocity.
Let's call Time with T.
Distance with Favour is (B + S) x T.
Distance against the stream is (B - S) x T.
Since the distance is twice if the stream is in favour
So, (B + S) x T = (B - S) x T x 2,
B + S = 2B - 2S,
B = 3S.
So, the ratio is 3 : 1.
Vikas said:
2 decades ago
How speed of boat in still water is (2x+x) /2 ?
Nithya said:
9 years ago
Thank you all for explaining the solution.
Niklu Rana said:
10 years ago
Let the speed of still water = X and the speed of stream = Y;
As given here, Speed against the stream = 1/2*(Speed in favor of the stream);
Therefor 2X-2Y = X+ Y;
So that, X/Y = 3/1.
As given here, Speed against the stream = 1/2*(Speed in favor of the stream);
Therefor 2X-2Y = X+ Y;
So that, X/Y = 3/1.
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