Finding number of path Help!!

Expert replies

anuu: Junior | Next Rank: 30 Posts; Posts: 13; Joined: Wed Feb 23, 2011 9:41 am; Thanked: 1 times

by anuu » Sun Jun 26, 2011 3:20 pm

Hi,

I came across the below problem in an online test. I got the wrong answer.
Any suggestion on the logic pls?

A person starts from A and passes through B and C,arrives D at last. If he go forward only to east and north, in how many way can he finish the trip?

a.20
b.32
c.36
d.56

Answer is c

My aprroach is: I came up with a grid comprising total of 6 moves(3 R's and 3Us) from A to D.

Hence total number of moves is 6c3 = 20 moves.

Can anybody pls explain the problem with the correct concept?

Regards,
Anu

Source: Beat The GMAT — Problem Solving | Sun Jun 26, 2011 3:20 pm

Frankenstein: Legendary Member; Posts: 1448; Joined: Tue May 17, 2011 9:55 amFollowed by: 53 members; Location: India; Thanked: 375 times

by Frankenstein » Mon Jun 27, 2011 9:28 pm

Hi,
There must some figure attached to this question. Otherwise, it is impossible to answer this question. Please attach the grid.

Cheers!

Things are not what they appear to be... nor are they otherwise

casperkamal: Junior | Next Rank: 30 Posts; Posts: 24; Joined: Mon May 31, 2010 3:29 am; Location: Hyderabad; Thanked: 2 times

by casperkamal » Tue Jun 28, 2011 3:02 am

Hi Anuu,

refer here...

https://www.beatthegmat.com/how-to-solve ... 86056.html

Kamal

arnabis2good: Junior | Next Rank: 30 Posts; Posts: 21; Joined: Tue Aug 21, 2007 7:41 pm; Thanked: 1 times

by arnabis2good » Tue Jun 28, 2011 6:22 pm

Can we not answer without the grid? There are 6 possible moves :

N-fwd, E-fwd, W-fwd, W-bckwd, S-fwd, S-bckwd

If there are 4 points in this trip, we have to select any 3. So the answer should be 6P3.

Do you see any issue with this approach?

Frankenstein: Legendary Member; Posts: 1448; Joined: Tue May 17, 2011 9:55 amFollowed by: 53 members; Location: India; Thanked: 375 times

by Frankenstein » Tue Jun 28, 2011 8:40 pm

arnabis2good wrote:Can we not answer without the grid? There are 6 possible moves :

N-fwd, E-fwd, W-fwd, W-bckwd, S-fwd, S-bckwd

If there are 4 points in this trip, we have to select any 3. So the answer should be 6P3.

Do you see any issue with this approach?

Hi,
This doesn't make sense at all to me. Without knowing the grid, there is no way one can solve as we do not know how many ways are there between two adjacent points. Moreover, you cannot justify your answer as well because your answer is not in options. So, that is at least some indication.

Cheers!

Things are not what they appear to be... nor are they otherwise

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