Aptitude - Boats and Streams - Discussion
Discussion Forum : Boats and Streams - General Questions (Q.No. 9)
9.
A man can row at 5 kmph in still water. If the velocity of current is 1 kmph and it takes him 1 hour to row to a place and come back, how far is the place?
Answer: Option
Explanation:
Speed downstream = (5 + 1) kmph = 6 kmph.
Speed upstream = (5 - 1) kmph = 4 kmph.
Let the required distance be x km.
| Then, | x | + | x | = 1 |
| 6 | 4 |
2x + 3x = 12
5x = 12
x = 2.4 km.
Discussion:
21 comments Page 2 of 3.
Vijaya said:
7 years ago
Hi friends, in the above explanations we have taken;
time = Distance/Speed
If we take,
distance = speed * time, then;
d=[(u+v)+(u-v)]t.
So, it becomes 10km. This will be the total distance covered by man(including coming back.)
if we want only the distance to a place then it will be 5km.
Why should we not consider this format? can anyone tell me?
time = Distance/Speed
If we take,
distance = speed * time, then;
d=[(u+v)+(u-v)]t.
So, it becomes 10km. This will be the total distance covered by man(including coming back.)
if we want only the distance to a place then it will be 5km.
Why should we not consider this format? can anyone tell me?
Agrim said:
8 years ago
Why do we need to calculate the downstream and upstream when we already the have speeds of boat(u) and speed of stream(v)? We can directly calculate the time from that.
Like-
u=5
v=1
t=1
Let the distance be x.
So x/5+x/1=1.
Solving the equation we will get the value of x which is 5/6.(but incorrect value).
Like-
u=5
v=1
t=1
Let the distance be x.
So x/5+x/1=1.
Solving the equation we will get the value of x which is 5/6.(but incorrect value).
Anil said:
1 decade ago
2x+3x=12
Is that multiplication of 2*3.
If yes, why we have to multiply 2*3 ?
Is that multiplication of 2*3.
If yes, why we have to multiply 2*3 ?
Utteya Pal said:
10 years ago
Easiest way to do this kind of problems:
{z(x^2-y^2)}/2x.
Here z= time taken to cover the both distance.
x = speed in still water.
y = speed of current.
{z(x^2-y^2)}/2x.
Here z= time taken to cover the both distance.
x = speed in still water.
y = speed of current.
Ashwin Hingole said:
1 decade ago
I think answer to how far is the place should be 1.2 km. And answer to how much distance man has covered should be 2.4 km. He goes and comes back. Suggestions please.
Kandarp Singh said:
1 decade ago
12 is the lcm of 4 and 6 and that expression solving is correct.
x/6 + x/4 = 1.
(4x+6x)/(6*4) = 1.
(2x+2x)/(3*4) = 1.
2x+3x = 12.
x/6 + x/4 = 1.
(4x+6x)/(6*4) = 1.
(2x+2x)/(3*4) = 1.
2x+3x = 12.
Shantanu datta said:
1 decade ago
From where is this 12 coming from?
2x+3x=6 after the first step.
2x+3x=6 after the first step.
Rakesh KIIT said:
1 decade ago
Average Speed during toatal journey=2(6)(4)/(6+4)
=4.8 kmph
so, Total distance coverd during the Journey=Time* Average speed
=1*4.8
=4.8km
so, How far is the place = 4.8/2
= 2.4 km
Because man goes and come back.
=4.8 kmph
so, Total distance coverd during the Journey=Time* Average speed
=1*4.8
=4.8km
so, How far is the place = 4.8/2
= 2.4 km
Because man goes and come back.
Dts said:
1 decade ago
Here we take lcm only.
Bhima God said:
1 decade ago
Mul of 6 and 4 should be 24 right?...how that 12 comes?
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