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Premutations and Combinations

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bowhag
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Premutations and Combinations [#permalink] New post   15 Jun 2020, 07:59
In the official guide they only go about explaining the premutations with repetition (n!) and Combinations without repetition (n! : k!(n-k)!.

Does this mean the other two (nPr & (k+n-1)! : k! (n-r)! ) are not used in the general questions and you don't need to know them?

Thanks in advance,

Bow
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EMPOWERgmatRichC
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Re: Premutations and Combinations [#permalink] New post   15 Jun 2020, 14:36
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Hi bowhag,

You're going to find that most GMAT questions are written so that they can be approached in more than one way. When dealing with any individual question, you have two goals: correctly answer the question, if possible (in a reasonable amount of time) and work in an efficient fashion. Thus, just because you correctly answer a question does not necessarily mean that there isn't something to be learned (such as a faster, more efficient approach).

Permutations and Combinations are relatively rare subjects on the GMAT - and sometimes you can approach them without using any formulas at all (although with certain Combination Formula questions, knowing the Combination Formula makes answering the question a LOT easier).

Since you're asking about some of the tougher concepts in the Quant section, how are you currently performing on all of the larger point-categories right now? How have you scored on your practice CATs/mocks? What is your overall goal score?

GMAT assassins aren't born, they're made,
Rich
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bowhag
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Re: Premutations and Combinations [#permalink] New post   15 Jun 2020, 23:34
Thanks for the response!

I did one mock a while ago and I didn't score very high on Quant, but honestly, I haven't done simple equations etc. for years now and never really learned it properly in secondary school (I wasn't the most active student back in the day if you get what I mean haha), so I'm revising the whole quant explanation at the moment.

even further so I can't remember if I even had these permutations and combination formulas at all in secondary school.

But again thank you for the answer! I also didn't think I really need a formula for it in general but since I'm learning everything again I want to learn it the proper way. So I think I just look at all of them but go into the ones mentioned in the official guide a bit deeper, but even if it doesn't appear on the GMAT, it's still good to learn.
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Re: Premutations and Combinations [#permalink] New post   16 Jun 2020, 01:09
bowhag wrote:
Thanks for the response!

I did one mock a while ago and I didn't score very high on Quant, but honestly, I haven't done simple equations etc. for years now and never really learned it properly in secondary school (I wasn't the most active student back in the day if you get what I mean haha), so I'm revising the whole quant explanation at the moment.

even further so I can't remember if I even had these permutations and combination formulas at all in secondary school.

But again thank you for the answer! I also didn't think I really need a formula for it in general but since I'm learning everything again I want to learn it the proper way. So I think I just look at all of them but go into the ones mentioned in the official guide a bit deeper, but even if it doesn't appear on the GMAT, it's still good to learn.

You will like the videos in this link.
https://gmatclub.com/forum/mgmat-study- ... 09197.html
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bowhag
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Schools: Georgetown MiM "23 (A$)
GPA: 3.93
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Re: Premutations and Combinations [#permalink] New post   16 Jun 2020, 02:19
@Inm87 Thank you! going to check them out!
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Re: Premutations and Combinations [#permalink] New post   16 Jun 2020, 20:13
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Hi bowhag,

Many GMATers find the Quant, the Verbal or both to be challenging, so you're not alone; in that same way, many GMATers are unhappy with their initial practice scores, but you really shouldn't be. That Score was just a measure of your skills right now - and you'll improve on that result over time as you learn more about the content, Tactics and little 'secrets' of the Exam. To make sure that you're studying in an effective and efficient fashion, it's important to define your practice performances, timeline and goals.

Studies:
1) How long have you studied? How many hours do you typically study each week?
2) What study materials have you used so far?
3) How did you score on that first CAT/mock (including the Quant and Verbal Scaled Scores)?

Goals:
4) What is your overall goal score?
5) When are you planning to take the GMAT?
6) When are you planning to apply to Business School and what Schools are you planning to apply to?

GMAT assassins aren't born, they're made,
Rich
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Re: Premutations and Combinations [#permalink]
16 Jun 2020, 20:13

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