1. Dismiss Notice
  2. Guest, be sure to check out How To Get Into Dental School, our free downloadable PDF with step-by-step details for dental school applicants!
    Dismiss Notice
  3. Dismiss Notice
  4. Download free Tapatalk for iPhone or Tapatalk for Android for your phone and follow the SDN forums with push notifications.
    Dismiss Notice

Destroyer QR ?

Discussion in 'DAT Discussions' started by Dentaholic, Jun 16, 2008.

  1. Dentaholic

    Joined:
    Jun 16, 2008
    Messages:
    5
    Likes Received:
    0
    Status:
    Pre-Dental
    Hi all! Im new to SDN, so sorry if this sounds confusing... I have a question about numbers 64, 20, and 27 of the QR in the Destroyer. How can you tell when you need to use the different equations?? 27-(n!/r!x(n-r)!) vs. 20-(n!/(n-r)!) vs. 64-(nCr)(p^n)((1-p)^r). Thanks! Im a little lost...
     
  2. Note: SDN Members do not see this ad.

  3. ET87

    5+ Year Member

    Joined:
    Jul 2, 2007
    Messages:
    29
    Likes Received:
    0
    Status:
    Pre-Dental
    For question 20, think "There are 8 horses that could place first, then if one places first, there are 7 horses that could place second, and then if that happens, there are 6 left that could place third". So for that one, the answer should be 8*7*6. This is an example of when Order matters. Like if Horse A gets in 1st place and horse B gets in second place, then that is a different scenario from if Horse B gets in first place and horse B gets in second, thus using nPr is appropriate and not nCr. You want to use nPr when order matters.

    I absolutely hate the way question 27 is worded. To me, there is only one combination of 3 Blue balloons you should be able to make, however the question implies that every blue balloon is different, and so the question is better worded like: Lynn has 12 Distinct Balloons, how many 3 balloon bouquets can she make? With this wording, it makes it more clear that you should use nCr because order DOES NOT matter, and a bouquet with balloons ABC is the same as a bouquet with balloons BCA. In this case use nCr or 11C3 = 220

    Question 64: I know this as a binomial distribution... I'm not sure if you learned it as this. So I'm not sure of an easy way to teach it.. =P Maybe you would not mind looking this up and seeing how it would fit with 3C2*(.70)^2*(.30)^1 =]

    Personally the wording of such questions like 27 made me stop doing those types of questions in the Destroyer.. they are a bit misleading.
     
  4. Dentaholic

    Joined:
    Jun 16, 2008
    Messages:
    5
    Likes Received:
    0
    Status:
    Pre-Dental
    THANKS SO MUCH! I really hate these kind of problems!!
     

Share This Page