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Path Example

by voodoo_child » Sun Nov 06, 2011 11:38 am
How many possible paths pass through O?

A) 84
B) 80
C) 40
D) 14
E) 24

OA - B. Any thoughts?

Here's what i did -
A to O => 5!/(3!*2!) = 10
O to B => 4!/(3!) = 4
Therefore, answer = 40
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by shankar.ashwin » Sun Nov 06, 2011 11:49 am
A to O is actually 6!/3!3!. 3 vertical/3 horizontal lines.
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by rijul007 » Sun Nov 06, 2011 11:54 am
shankar.ashwin wrote:A to O is actually 6!/3!3!. 3 vertical/3 horizontal lines.
you are ignoring the possibility of going to the 4th horizontal line and coming back to 3rd
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by shankar.ashwin » Sun Nov 06, 2011 11:56 am
Well, I assume it asks for the shortest distance, it not you could go round and round, you can never come up with an answer :)
rijul007 wrote:
shankar.ashwin wrote:A to O is actually 6!/3!3!. 3 vertical/3 horizontal lines.
you are ignoring the possibility of going to the 4th horizontal line and coming back to 3rd
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by rijul007 » Sun Nov 06, 2011 11:59 am
shankar.ashwin wrote:Well, I assume it asks for the shortest distance, it not you could go round and round, you can never come up with an answer :)
rijul007 wrote:
shankar.ashwin wrote:A to O is actually 6!/3!3!. 3 vertical/3 horizontal lines.
you are ignoring the possibility of going to the 4th horizontal line and coming back to 3rd
If it were about the shotest distance, than answer would have been 24

But that's not it!
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by rijul007 » Sun Nov 06, 2011 12:06 pm
rijul007 wrote:
shankar.ashwin wrote:Well, I assume it asks for the shortest distance, it not you could go round and round, you can never come up with an answer :)
rijul007 wrote:
shankar.ashwin wrote:A to O is actually 6!/3!3!. 3 vertical/3 horizontal lines.
you are ignoring the possibility of going to the 4th horizontal line and coming back to 3rd
If it were about the shotest distance, than answer would have been 24

But that's not it!

Oops i'm sorry, actually it IS asking forthe shortest distance!!

I committed a blunder here..

A-0 => 20 ways
O-B => 4 ways

A-O-B => 20*4 (Earlier, I added them by mistake)
=>80

Option B
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by voodoo_child » Sun Nov 06, 2011 1:32 pm
How did you guys get 20*4?

HEre's the corrected figure.
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by rijul007 » Sun Nov 06, 2011 1:56 pm
voodoo_child wrote:How did you guys get 20*4?

HEre's the corrected figure.

Image

We were working on a wrong figure all along.
Not cool. :shock:
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by shankar.ashwin » Sun Nov 06, 2011 9:28 pm
I don't see anything wrong with what you did;

5C3 * 4C1 = 40. should be C IMO.

Could you post the full question, as this one seems incomplete. It never mentions shortest route, maybe they ask for something else here.
voodoo_child wrote:How did you guys get 20*4?

HEre's the corrected figure.
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by phelps » Mon Nov 07, 2011 2:29 am
Can anyone explain this question to me please!!
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by GMATGuruNY » Mon Nov 07, 2011 8:29 am
phelps wrote:Can anyone explain this question to me please!!
I posted a solution to a similar problem here:

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