Aptitude - Boats and Streams - Discussion

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"Nothing in life is to be feared, it is only to be understood."

- Marie Curie

In one hour, a boat goes 11 km/hr along the stream and 5 km/hr against the stream. The speed of the boat in still water (in km/hr) is:

[A].	3 km/hr	[B].	5 km/hr
[C].	8 km/hr	[D].	9 km/hr

Answer: Option B

Explanation:

Speed in still water = 1 (11 + 5) kmph = 8 kmph.

2

Vivek Patidar said: (Mon, Sep 5, 2011 06:19:27 PM)

Because in the condition of still position of water the speed one side and opposite side of water will be equal thats why we will take average of both speed.

Manjit Singh said: (Thu, Sep 15, 2011 01:07:26 PM)

Here speed along the stream and against the stream is given. Then how can we assume water to be steady (both the ways). Then why this 1/2 has come?

Debapriya Dandapat said: (Sat, Sep 17, 2011 01:38:17 AM)

Upstream relative speed is u + v=11km/hr Downstream speed is u-v=5 Where u= speed of boat in still water and v is speed of stream So adding two equations u+v + u-v =11+5 2u=16 So, u=8.

Ajit Jha(Iit Kharagpur) said: (Fri, Dec 30, 2011 12:29:14 AM)

This Q is wrong buddy... Here in stream dir. it takes 1 hour and again in downstream it takes 1 hour. Then.. x+y=11/1=11------(1) x-y=5/1=5----(2) fm eq. 1 & 2.. we get.. x=8 km/h