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?
2.4 km
2.5 km
3 km
3.6 km
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.

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.

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.

Rishita Burman said:   4 years ago
@Bhima,

You need to find out the L.C.M of the denominators. We multiply the denominator when L.C.M is not possible.
(1)

Rishita Burman said:   4 years ago
@Bhima,

You need to find out the L.C.M of the denominators. We multiply the denominator when L.C.M is not possible.
(3)

Sasikumar said:   1 decade ago
Speed downstream = (5 + 1) kmph = 6 kmph.

Speed upstream = (5 - 1) kmph = 4 kmph.

average speed=2(6)(4)/(6+4)

Sam said:   1 decade ago
(4x+6x)/(6*4) = 1.
4x+6x = 24.

10x = 24.
x = 24/10.
x = 2.4.

I hope You are all understand.
(1)

Anil said:   1 decade ago
2x+3x=12

Is that multiplication of 2*3.

If yes, why we have to multiply 2*3 ?

Shantanu datta said:   1 decade ago
From where is this 12 coming from?

2x+3x=6 after the first step.

Bhima God said:   1 decade ago
Mul of 6 and 4 should be 24 right?...how that 12 comes?

Dts said:   1 decade ago
Here we take lcm only.


Post your comments here:

Your comments will be displayed after verification.