Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

A certain stock exchange designates each stock with a 1, 2 [#permalink]

Show Tags

26 Oct 2009, 13:25

3

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

35% (medium)

Question Stats:

68% (02:26) correct
32% (02:01) wrong based on 391 sessions

HideShow timer Statistics

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?

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.

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]

Show Tags

02 Dec 2013, 01:01

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).

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.
_________________

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]

Show Tags

08 Dec 2014, 11:40

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.
_________________

A certain stock exchange designates each stock with a 1, 2 [#permalink]

Show Tags

23 Dec 2015, 10:58

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.)

Total =26+26^2+26^3 =18,278

Possibly foolish question, but why are we adding instead of multiplying the 26's? I've been doing all these combinatorics questions and it's almost always multiplying possibilities not adding them. Just curious what the difference is that changes why we'd add versus multiply in these kinds of situations.
_________________

Re: A certain stock exchange designates each stock with a 1, 2 [#permalink]

Show Tags

23 Dec 2015, 12:41

what about the case of AA, BB, CC...Wouldn't we have to consider these as 1 instead of double counting them.

I had them as 26+(26*26/2)+(26*26*26)/6. What am I doing wrong?

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.)

Total =26+26^2+26^3 =18,278

gmatclubot

Re: A certain stock exchange designates each stock with a 1, 2
[#permalink]
23 Dec 2015, 12:41

Hey, guys, So, I’ve decided to run a contest in hopes of getting the word about the site out to as many applicants as possible this application season...

Whether you’re an entrepreneur, aspiring business leader, or you just think that you may want to learn more about business, the thought of getting your Masters in Business Administration...

Whether you’re an entrepreneur, aspiring business leader, or you just think that you may want to learn more about business, the thought of getting your Masters in Business Administration...