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A certain stock exchange designates each stock with a 1, 2 [#permalink]
26 Oct 2009, 12:25

2

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

35% (medium)

Question Stats:

70% (02:30) correct
30% (01:57) wrong based on 180 sessions

A certain stock exchange designates each stock with a 1, 2 or 3 letter code, where each letter is selected from the 26 letters of the alphabet. If the letters may be repeated and if the same letters used in a different order, constitute a different code, how many diff stocks is it possible to designate with these codes?

Re: Combinations - Powerprep [#permalink]
26 Oct 2009, 12:40

I think that I should be using permutations as order does matter here, but I am still not getting the answer: P of 26 taken by 3 = 15,600 P of 26 taken by 2 = 650 P of 26 taken by 1 = 26 adding them does not give me the right answer still.

Re: Combinations - Powerprep [#permalink]
26 Oct 2009, 13:08

2

This post received KUDOS

Expert's post

1

This post was BOOKMARKED

ralucaroman wrote:

HI,

Can smb please help me to understand the below problem?

A certain stock exchange designates each stock with a 1, 2 or 3 letter code, where each letter is selected from the 26 letters of the alphabet. If the letters may be repeated and if the same letters used in a different order, constitute a different code, how many diff stocks is it possible to designate with these codes? A: 2,951 B: 8,125 C:15,600 D: 16,302 E: 18,278

They say that QA is E, however I am not sure how to get there.

I have C 26 taken by 3 = 2,600 C of 26 taken by 2 = 325 C of 26 taken by 1 = 26. If I add these, I get answer A. Not sure what I am doing wrong.

Thank you, Andreea

1 letter code - 26 (or you can write 26C1) 2 letter code - 26*26=26^2 (or you can write 26C1*26C1=26^2) 3 letter code - 26*26*26=26^3 (or you can write 26C1*26C1*26C1=26^3)

(For 2 letter, for example, you have 26 choices per each letter, it's 26^2 and not 26C2 or 26P2.)

Re: A certain stock exchange designates each stock with a 1, 2 [#permalink]
02 Dec 2013, 00:01

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: Combinations - Powerprep [#permalink]
02 Dec 2013, 00:47

Expert's post

1

This post was BOOKMARKED

Bunuel wrote:

ralucaroman wrote:

HI,

Can smb please help me to understand the below problem?

A certain stock exchange designates each stock with a 1, 2 or 3 letter code, where each letter is selected from the 26 letters of the alphabet. If the letters may be repeated and if the same letters used in a different order, constitute a different code, how many diff stocks is it possible to designate with these codes? A: 2,951 B: 8,125 C:15,600 D: 16,302 E: 18,278

They say that QA is E, however I am not sure how to get there.

I have C 26 taken by 3 = 2,600 C of 26 taken by 2 = 325 C of 26 taken by 1 = 26. If I add these, I get answer A. Not sure what I am doing wrong.

Thank you, Andreea

1 letter code - 26 (or you can write 26C1) 2 letter code - 26*26=26^2 (or you can write 26C1*26C1=26^2) 3 letter code - 26*26*26=26^3 (or you can write 26C1*26C1*26C1=26^3)

(For 2 letter, for example, you have 26 choices per each letter, it's 26^2 and not 26C2 or 26P2.)

Re: A certain stock exchange designates each stock with a 1, 2 [#permalink]
08 Dec 2014, 10:40

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email. _________________

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