It is currently 20 Oct 2017, 04:07

GMAT Club Daily Prep

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

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Arran x items from a collection of N

Author Message
Manager
Joined: 15 Jul 2008
Posts: 205

Kudos [?]: 68 [0], given: 0

Arran x items from a collection of N [#permalink]

Show Tags

05 Aug 2008, 06:18
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

[edited once]

Guys,

I am having some confusion over this question

How many 3 letter words (arrangements) can you form with alphabet drawn from aabbbccccdddeefffgg

For such a case is there an expression similar to the one for following case ?..

how many ways can you arrange all of them, answer = 19!/2!3!4!3!2!3!2!

Last edited by bhushangiri on 05 Aug 2008, 07:44, edited 1 time in total.

Kudos [?]: 68 [0], given: 0

Senior Manager
Joined: 07 Jul 2005
Posts: 402

Kudos [?]: 61 [0], given: 0

Re: Arran x items from a collection of N [#permalink]

Show Tags

05 Aug 2008, 07:10
I think the way to approach the first question is that you notice that there are only 3 letters to choose from.

So, with three different letters, you can choose from 3 letters for the first space, 3 letters for the second space, and 3 letters for the second space. That's 3x3x3=27.
Since 'aaa' is not possible, then it's 27-1 = 26 arrangements.

Kudos [?]: 61 [0], given: 0

Manager
Joined: 15 Jul 2008
Posts: 205

Kudos [?]: 68 [0], given: 0

Re: Arran x items from a collection of N [#permalink]

Show Tags

05 Aug 2008, 07:38
rigger wrote:
I think the way to approach the first question is that you notice that there are only 3 letters to choose from.

So, with three different letters, you can choose from 3 letters for the first space, 3 letters for the second space, and 3 letters for the second space. That's 3x3x3=27.
Since 'aaa' is not possible, then it's 27-1 = 26 arrangements.

Thanks. But i am looking for a more generic expression. Like n!/(a!b!) is for arranging all the given items.

I am editing the question to reflect that possibility also.

Kudos [?]: 68 [0], given: 0

Senior Manager
Joined: 07 Jul 2005
Posts: 402

Kudos [?]: 61 [0], given: 0

Re: Arran x items from a collection of N [#permalink]

Show Tags

05 Aug 2008, 08:33
n!/(a!b!....) is the general expression. There's nothing more to it than that.

Kudos [?]: 61 [0], given: 0

Manager
Joined: 15 Jul 2008
Posts: 205

Kudos [?]: 68 [0], given: 0

Re: Arran x items from a collection of N [#permalink]

Show Tags

05 Aug 2008, 08:39
rigger wrote:
n!/(a!b!....) is the general expression. There's nothing more to it than that.

But that is only if you arrange all n. Not if you take some from the n and try to arrange.

Kudos [?]: 68 [0], given: 0

Re: Arran x items from a collection of N   [#permalink] 05 Aug 2008, 08:39
Display posts from previous: Sort by