Aptitude - Boats and Streams - Discussion
Discussion Forum : Boats and Streams - General Questions (Q.No. 15)
15.
A man rows to a place 48 km distant and come back in 14 hours. He finds that he can row 4 km with the stream in the same time as 3 km against the stream. The rate of the stream is:
Answer: Option
Explanation:
Suppose he move 4 km downstream in x hours. Then,
| Speed downstream = |  |
4 |  |
km/hr. |
| x |
| Speed upstream = | |
3 | |
km/hr. |
| x |
 |
48 | + | 48 | = 14 or x = | 1 | . |
| (4/x) | (3/x) | 2 |
So, Speed downstream = 8 km/hr, Speed upstream = 6 km/hr.
| Rate of the stream = | 1 | (8 - 6) km/hr = 1 km/hr. |
| 2 |
Discussion:
48 comments Page 3 of 5.
Shanur Rahman said:
8 years ago
Suppose it took him x hrs to go downstream, then it will take him 14-x upstream. Therefore x/ (14-x) = 3/4.
There you go.
There you go.
Priya said:
8 years ago
Distance=48 km in 14 hours.
rate of stream = x.
downstream=4 km (with the water).
Upstream =3 km(against the water).
Rate of the stream =1/2(4-3)=1/2.
Therefore x=1/2.
Then,4/1/2 =4 * 2 = 8.
Then,3/1/2 = 3 * 2 = 6.
So,1/2(8-6) = 1/2(2)
Answer is 1.
rate of stream = x.
downstream=4 km (with the water).
Upstream =3 km(against the water).
Rate of the stream =1/2(4-3)=1/2.
Therefore x=1/2.
Then,4/1/2 =4 * 2 = 8.
Then,3/1/2 = 3 * 2 = 6.
So,1/2(8-6) = 1/2(2)
Answer is 1.
Pouvanam said:
9 years ago
How do you find the value of x?
Nessa said:
9 years ago
How did you get x = 1/2? I got it as 2.
Max said:
9 years ago
A man can row 24 km upstream and 54 km downstream in 6 hours. He can also row 36 km upstream and 48 km downstream in 8 hours. What is the speed of the man in still water?
Kiran said:
9 years ago
This can also be solved using Avg speed concept.
Let t be time taken.
Let x be stream speed & v be boat speed.
Total distance = 48 + 48 = 96.
Time = 14 hrs.
So, 96/14 = 2ab/(a+b) = 2((4/t*3/t)).
==> 7/t.
Solving we get t = 1/2 hr.
=> 4/(1/2) = 8.
=> 3/(1/2) = 6.
So, v+x = 8 & v - x =6.
Solving we get v=7 : x=1.
Stream speed = 1/2 (8 - 6) = 1 km/hr.
Let t be time taken.
Let x be stream speed & v be boat speed.
Total distance = 48 + 48 = 96.
Time = 14 hrs.
So, 96/14 = 2ab/(a+b) = 2((4/t*3/t)).
==> 7/t.
Solving we get t = 1/2 hr.
=> 4/(1/2) = 8.
=> 3/(1/2) = 6.
So, v+x = 8 & v - x =6.
Solving we get v=7 : x=1.
Stream speed = 1/2 (8 - 6) = 1 km/hr.
Pulak sarkar said:
9 years ago
Downstream 4/x = 4/1/2 = 4*2 = 8kmph.
Upstream 3/x = 3/1/2 = 3*2 = 6kmph.
Upstream 3/x = 3/1/2 = 3*2 = 6kmph.
Chirag gupta said:
1 decade ago
Why we divide this by x?
I think answer should be 2 km/hr.
I think answer should be 2 km/hr.
Aparna said:
1 decade ago
How did you got that x=12 I think x=7/14 so x=1/2?
Can you explain me is it right are wrong please?
Can you explain me is it right are wrong please?
Rishi said:
1 decade ago
Let rate of stream and still water be v km/hr and u km/hr respectively.
So speed in downstream = u+v km/hr.
Speed in upstream = u-v km/hr.
In question distance traveled in both direction is same = 48 Km.
So 4/u+v = 4/u-v.
=> u/v = 7/1.
Now we can say u = 7k & v = k.
So time of downstream = 48/8k = 6/k and time in upstream = 48/6k = 8/k.
Now from question time up + time down = 14hr.
So (8/k)+(6/k) = 14 => k = 1. So u = 7 km/h.
And v = 1 km/h answer.
So speed in downstream = u+v km/hr.
Speed in upstream = u-v km/hr.
In question distance traveled in both direction is same = 48 Km.
So 4/u+v = 4/u-v.
=> u/v = 7/1.
Now we can say u = 7k & v = k.
So time of downstream = 48/8k = 6/k and time in upstream = 48/6k = 8/k.
Now from question time up + time down = 14hr.
So (8/k)+(6/k) = 14 => k = 1. So u = 7 km/h.
And v = 1 km/h answer.
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