Free GRE Prep Hour: Probability: Basic, Combination, and Estimation

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  • Опубліковано 23 гру 2024

КОМЕНТАРІ • 15

  • @ibrahimgadli2583
    @ibrahimgadli2583 3 місяці тому

    What is the chance that each roll is at least 3? for this question while using the total - opposite method I am getting 8/9 as the ans

  • @rashmiyeole7784
    @rashmiyeole7784 4 роки тому +2

    Can you please upload a video for standard deviation? Will be very helpful.

  • @samuelwilson3461
    @samuelwilson3461 4 роки тому +2

    @53:43 why is the answer not 6/36?
    Can't you roll a 4, 4 two ways? For example: 6, 2 can also be rolled 2, 6. Why can't 4, 4 be treated the same way?

    • @manhattanprepgre7390
      @manhattanprepgre7390  4 роки тому +2

      Excellent question! We actually can't count identical rolls as interchangeable. The idea is that 2,6 and 6,2 actually represent two different things that can happen: 2 on the first roll & 6 on the second, or 6 on the first roll & 2 on the second. This means there are two possible first rolls that would get us to our result; the results are equivalent, but not identical. If we roll a 2 (which has a 1/6 chance), we can get to 8 by rolling 6 next (1/6 chance of that, so 1/36 chance of 2,6). If we roll a 6 (an additional 1/6 chance), we can get to 8 by rolling 2 next (making an extra 1/36 chance of getting 8 with 2 and 6). By contrast, there's only one way to get 4,4. We have to roll 4 both times. There's only one initial roll (4) that would work and only one follow-up that will get us what we want, so our chance of 4,4 is half that of 6,2/2,6. Hope that helps clarify!

    • @samuelwilson3461
      @samuelwilson3461 4 роки тому

      @@manhattanprepgre7390 Thanks!

  • @jessica3499
    @jessica3499 3 роки тому +3

    In the last question, there is a much simpler method for the same.
    Probability that the first person is a part of a couple * Probability of the first winner's partner winning
    1 *1/19 = 1/19

    • @manhattanprepgre7390
      @manhattanprepgre7390  3 роки тому

      Hi Jessica. Exactly! That's the approach Dmitry recommends at 1:06:20!

  • @Raseed-oe2cy
    @Raseed-oe2cy 4 роки тому +2

    could you please add standard deviation basic concept and also do solve some problems!!!!!!!!!!!!!!!!

    • @manhattanprepgre7390
      @manhattanprepgre7390  4 роки тому

      Thanks for the feedback! I'll pass it along to our Instructor team.

  • @premanne5943
    @premanne5943 3 роки тому

    at 43.51, sum of probability of getting both times 3 + neither times 3 + one time 3 is not equal to 1. i think probability of one time 3 is 10/36.

    • @manhattanprepgre7390
      @manhattanprepgre7390  3 роки тому

      Watch the phrasing on that second question. We're looking at the chance of AT LEAST ONE 3. That could be one 3 or two 3's. So the second probability (11/36) is inclusive of the first (1/36). If we add 11/36 and 25/36, we do get 1, since we will always get either NO 3 or AT LEAST ONE 3.

  • @mohammedshoab2778
    @mohammedshoab2778 4 роки тому +1

    This is pure gold!!

  • @MicroLiberman
    @MicroLiberman 2 роки тому +5

    Not a good teacher. Very confusing!

  • @sujaanaryal6355
    @sujaanaryal6355 3 роки тому

    Superb! You guys are doing an amazing job. Keep it up!!