• Economist Test Prep
    Free Trial & Practice Exam
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    Economist Test Prep
  • PrepScholar GMAT
    5 Day FREE Trial
    Study Smarter, Not Harder

    Available with Beat the GMAT members only code

    MORE DETAILS
    PrepScholar GMAT
  • Veritas Prep
    Free Veritas GMAT Class
    Experience Lesson 1 Live Free

    Available with Beat the GMAT members only code

    MORE DETAILS
    Veritas Prep
  • Magoosh
    Magoosh
    Study with Magoosh GMAT prep

    Available with Beat the GMAT members only code

    MORE DETAILS
    Magoosh
  • Target Test Prep
    5-Day Free Trial
    5-day free, full-access trial TTP Quant

    Available with Beat the GMAT members only code

    MORE DETAILS
    Target Test Prep
  • Varsity Tutors
    Award-winning private GMAT tutoring
    Register now and save up to $200

    Available with Beat the GMAT members only code

    MORE DETAILS
    Varsity Tutors
  • EMPOWERgmat Slider
    1 Hour Free
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    EMPOWERgmat Slider
  • Kaplan Test Prep
    Free Practice Test & Review
    How would you score if you took the GMAT

    Available with Beat the GMAT members only code

    MORE DETAILS
    Kaplan Test Prep
  • e-gmat Exclusive Offer
    Get 300+ Practice Questions
    25 Video lessons and 6 Webinars for FREE

    Available with Beat the GMAT members only code

    MORE DETAILS
    e-gmat Exclusive Offer

question about combinations and permusation

This topic has 6 expert replies and 2 member replies
svbla Newbie | Next Rank: 10 Posts
Joined
15 May 2009
Posted:
5 messages

question about combinations and permusation

Post Fri Apr 01, 2016 12:28 pm
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    I have two questions don't get it. can someone explain here? thanks!


    5. How many different four-letter passwords can be created for a software access if no letter can be used more than once?

    6.How many different ways you can elect a Chairman and Co-Chairman of a committee if you have 10 people to choose from.

    my answer were:
    5: 26C4
    6: 10C2

    because I don't think the order matters here, it didn't say anything about orders!
    well the correct answers are 26P4 and 10P2.

    Can someone explain it to me why the order matters in these two questions??
    Thanks!!

    Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums!
    Post Fri Apr 01, 2016 2:26 pm
    Hi svbla,

    If these are GMAT questions, then you should make sure to list the 5 answer choices. In addition, you should list questions individually, so that the discussion can stay focused on one prompt.

    Regarding these two prompts, they are both Permutations (since the order of the items matters.

    In question #5, passwords are unique (meaning that "abcd" is NOT the same as "dcba"), so the number of passwords (if letters CANNOT be used more than once) is (26)(25)(24)(23)

    In question #6, the two "titles" are "Chairman" and "Co-Chairman", so choosing "A" for chairman and "B" for co-chairman is NOT the same as choosing "B" for chairman and "A" for co-chairman. As such, the possible arrangements are (10)(9) = 90.

    IF... in question #6, you were selecting two "co-chairman" (meaning that both people would receive the same title), THEN you would have a Combination and the answer would be 10c2.

    GMAT assassins aren't born, they're made,
    Rich

    _________________
    Contact Rich at Rich.C@empowergmat.com

    Post Sat Apr 02, 2016 12:43 pm
    As Rich pointed out, order DOES matter in both of these cases. Here's a way to help you remember...

    Order DOESN'T matter if you could shuffle all of the positions around and still have the same grouping. The terms that will be most often used here:
    - GROUP
    - COMMITTEE
    - TEAM
    - MIXTURE (e.g. adding items to a fruit salad)

    Order DOES matter whenever specific positions are specified / implied. Here are the most common types:
    - PASSWORD COMBINATIONS
    - ARRANGEMENTS (pictures on a wall, people in a seating chart, letters in a word, etc)
    - RANKINGS (gold/silver/bronze, 1st/2nd/3rd place finish, president/vice president, etc)

    _________________


    Ceilidh Erickson
    Manhattan Prep GMAT & GRE instructor
    EdM in Mind, Brain, and Education
    Harvard Graduate School of Education


    Manhattan Prep instructors all have 99th+ percentile scores and expert teaching experience.
    Sign up for a FREE TRIAL, and learn why we have the highest ratings in the GMAT industry!

    Free Manhattan Prep online events - The first class of every online Manhattan Prep course is free. Classes start every week.

    GMAT/MBA Expert

    Post Thu May 11, 2017 8:24 pm
    The order definitely matters! If Mark is the chairman and Dave is the co-chairman, we've got a different leadership team than we'd have if Dave is the chairman and Mark is the co-chairman: in the first case, Mark has final say, but in the second, Dave does.

    So many of the problems in the world come down to this, don't they? Smile

    Enroll in a Veritas Prep GMAT class completely for FREE. Wondering if a GMAT course is right for you? Attend the first class session of an actual GMAT course, either in-person or live online, and see for yourself why so many students choose to work with Veritas Prep. Find a class now!
    Post Mon Jun 05, 2017 6:35 pm
    Matt@VeritasPrep wrote:
    The order definitely matters! If Mark is the chairman and Dave is the co-chairman, we've got a different leadership team than we'd have if Dave is the chairman and Mark is the co-chairman: in the first case, Mark has final say, but in the second, Dave does.

    So many of the problems in the world come down to this, don't they? Smile
    Hm, yes - I'd say that a lot of the problems in the world come down to all-male leadership teams Wink

    _________________


    Ceilidh Erickson
    Manhattan Prep GMAT & GRE instructor
    EdM in Mind, Brain, and Education
    Harvard Graduate School of Education


    Manhattan Prep instructors all have 99th+ percentile scores and expert teaching experience.
    Sign up for a FREE TRIAL, and learn why we have the highest ratings in the GMAT industry!

    Free Manhattan Prep online events - The first class of every online Manhattan Prep course is free. Classes start every week.

    GMAT/MBA Expert

    Post Mon Jun 05, 2017 11:56 pm
    ceilidh.erickson wrote:
    Hm, yes - I'd say that a lot of the problems in the world come down to all-male leadership teams Wink
    Hey, if they're chairman and co-chairman of, say, the Flat Earth Society, I'd think we want the most problematic leadership possible. ó‿ó

    Thanked by: ceilidh.erickson
    Enroll in a Veritas Prep GMAT class completely for FREE. Wondering if a GMAT course is right for you? Attend the first class session of an actual GMAT course, either in-person or live online, and see for yourself why so many students choose to work with Veritas Prep. Find a class now!

    Top Member

    elias.latour.apex Master | Next Rank: 500 Posts
    Joined
    20 Apr 2017
    Posted:
    126 messages
    Followed by:
    1 members
    Thanked:
    25 times
    GMAT Score:
    770
    Most Thanked Member Most Responsive Member
    Post Mon Jun 19, 2017 3:22 am
    ceilidh.erickson wrote:
    Matt@VeritasPrep wrote:
    The order definitely matters! If Mark is the chairman and Dave is the co-chairman, we've got a different leadership team than we'd have if Dave is the chairman and Mark is the co-chairman: in the first case, Mark has final say, but in the second, Dave does.

    So many of the problems in the world come down to this, don't they? Smile
    Hm, yes - I'd say that a lot of the problems in the world come down to all-male leadership teams Wink
    Are you assuming their gender?

    _________________
    Elias Latour
    Verbal Specialist @ ApexGMAT
    blog.apexgmat.com
    +1 (646) 736-7622

    GMAT/MBA Expert

    Post Wed Jun 21, 2017 4:25 pm
    elias.latour.apex wrote:
    ceilidh.erickson wrote:
    Matt@VeritasPrep wrote:
    The order definitely matters! If Mark is the chairman and Dave is the co-chairman, we've got a different leadership team than we'd have if Dave is the chairman and Mark is the co-chairman: in the first case, Mark has final say, but in the second, Dave does.

    So many of the problems in the world come down to this, don't they? Smile
    Hm, yes - I'd say that a lot of the problems in the world come down to all-male leadership teams Wink
    Are you assuming their gender?
    You know, I pondered that riff myself, but I couldn't find any languages/cultures in which Mark and Dave were female names. (You'd think Davé would be a female name somewhere, but I couldn't find it.)

    Enroll in a Veritas Prep GMAT class completely for FREE. Wondering if a GMAT course is right for you? Attend the first class session of an actual GMAT course, either in-person or live online, and see for yourself why so many students choose to work with Veritas Prep. Find a class now!

    Top Member

    elias.latour.apex Master | Next Rank: 500 Posts
    Joined
    20 Apr 2017
    Posted:
    126 messages
    Followed by:
    1 members
    Thanked:
    25 times
    GMAT Score:
    770
    Most Thanked Member Most Responsive Member
    Post Thu Jun 22, 2017 3:54 am
    Matt@VeritasPrep wrote:
    elias.latour.apex wrote:
    ceilidh.erickson wrote:
    Matt@VeritasPrep wrote:
    The order definitely matters! If Mark is the chairman and Dave is the co-chairman, we've got a different leadership team than we'd have if Dave is the chairman and Mark is the co-chairman: in the first case, Mark has final say, but in the second, Dave does.

    So many of the problems in the world come down to this, don't they? Smile
    Hm, yes - I'd say that a lot of the problems in the world come down to all-male leadership teams Wink
    Are you assuming their gender?
    You know, I pondered that riff myself, but I couldn't find any languages/cultures in which Mark and Dave were female names. (You'd think Davé would be a female name somewhere, but I couldn't find it.)
    You're mistaken because you are confusing gender with sex. They are not the same. Dave could easily be a pre-op transgender woman trapped in a man's body.

    _________________
    Elias Latour
    Verbal Specialist @ ApexGMAT
    blog.apexgmat.com
    +1 (646) 736-7622

    Best Conversation Starters

    1 Vincen 152 topics
    2 lheiannie07 61 topics
    3 Roland2rule 49 topics
    4 LUANDATO 44 topics
    5 ardz24 40 topics
    See More Top Beat The GMAT Members...

    Most Active Experts

    1 image description Brent@GMATPrepNow

    GMAT Prep Now Teacher

    140 posts
    2 image description Rich.C@EMPOWERgma...

    EMPOWERgmat

    110 posts
    3 image description EconomistGMATTutor

    The Economist GMAT Tutor

    109 posts
    4 image description GMATGuruNY

    The Princeton Review Teacher

    107 posts
    5 image description DavidG@VeritasPrep

    Veritas Prep

    72 posts
    See More Top Beat The GMAT Experts