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Josh has to run an electrical wire from point a to point b [#permalink]
28 Aug 2010, 08:58

00:00

A

B

C

D

E

Difficulty:

25% (low)

Question Stats:

68% (01:26) correct
31% (01:23) wrong based on 95 sessions

Attachment:

picture.jpg [ 2.53 KiB | Viewed 1996 times ]

Josh has to run an electrical wire from point a to point b along a circuit that is restricted to the grid shown to the left. How many possible paths could Josh use that have the minimum possible length?

Re: Grockit: similar to OG Quant qustion [#permalink]
28 Aug 2010, 09:05

6

This post received KUDOS

Expert's post

zisis wrote:

Josh has to run an electrical wire from point a to point b along a circuit that is restricted to the grid shown to the left. How many possible paths could Josh use that have the minimum possible length?

A 8 B 10 C 12 D 15 E 16

obv the answer can be found by counting the routes, but is there a better way?

You can notice that in order the length to be minimum wire should only go UP and RIGHT: namely twice UP and 4 times RIGHT.

So combination of UURRRR: # of permutations of 6 letters out of which there are 2 identical U's and 4 identical R's is \frac{6!}{2!4!}=15.

Re: Grockit: similar to OG Quant qustion [#permalink]
29 Aug 2010, 04:48

Bunuel wrote:

zisis wrote:

Josh has to run an electrical wire from point a to point b along a circuit that is restricted to the grid shown to the left. How many possible paths could Josh use that have the minimum possible length?

A 8 B 10 C 12 D 15 E 16

obv the answer can be found by counting the routes, but is there a better way?

You can notice that in order the length to be minimum wire should only go UP and RIGHT: namely twice UP and 4 times RIGHT.

So combination of UURRRR: # of permutations of 6 letters out of which there are 2 identical U's and 4 identical R's is \frac{6!}{2!4!}=15.

Answer: D.

Hope it's clear.

thanks! thats exactly what i was looking for ! If i recall correcty, you must be the GMATclub combinations expert

[ IDEA how about we have experts stamps for certain individuals ! SC, combinations, RC, algebra etc....something the forum admins should consider...]

find the no of ways [#permalink]
23 Oct 2010, 05:48

hi all please explain .. if there is a rectangle and this rectangle is divided in to four equal rectangles by building roads inside it then how many ways are there with which one can reach from one corner to other diagonally opposite corner. please try to explain in terms of combinations .like in terms of nCr etc.

Re: find the no of ways [#permalink]
23 Oct 2010, 09:11

harshsingla wrote:

hi all please explain .. if there is a rectangle and this rectangle is divided in to four equal rectangles by building roads inside it then how many ways are there with which one can reach from one corner to other diagonally opposite corner. please try to explain in terms of combinations .like in terms of nCr etc.

thanks

You need to find permutations of UURR = 4!/2!2! = 6
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Re: find the no of ways [#permalink]
23 Oct 2010, 09:27

harshsingla wrote:

but how 4c2..??? please explain!!

think of it like this You have four moves to make to reach the opposite corner

two moves are up and two moves are right

now, any order of moves would always get to the corner

the question really is that out of move1,2,3&4 which two you pick to be the Up move (the other two will be the right move). The ways to do this is C(4,2), choosing 2 out of 4.
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Re: Josh has to run an electrical wire from point a to point b [#permalink]
18 Jan 2014, 07:16

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