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.
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.
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.
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.
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?
Nessa said:
9 years ago
How did you get x = 1/2? I got it as 2.
Pouvanam said:
9 years ago
How do you find the value of x?
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.
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.
Subhrasubha priyadarsini said:
8 years ago
4/x+y=3/x-y,
4x-4y=3x+,
x=7y -----> eq1
48/x+y +48/x-y =14,
48/8y+48/6y=14,
14/y=14,
y=1,
Now x=7.
4x-4y=3x+,
x=7y -----> eq1
48/x+y +48/x-y =14,
48/8y+48/6y=14,
14/y=14,
y=1,
Now x=7.
Divya said:
8 years ago
Given : 4/x+y = 3/x-y --> (1).
by solving the eq > x =7y.
and : 48/x-y + 48/x+y = 14.
48//7y-y + 48/7y+y = 14.
48/6y + 48/8y = 14.
8 + 6 =14y,
14 =14y,
y = 1km/hr.
by solving the eq > x =7y.
and : 48/x-y + 48/x+y = 14.
48//7y-y + 48/7y+y = 14.
48/6y + 48/8y = 14.
8 + 6 =14y,
14 =14y,
y = 1km/hr.
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