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Probability question....?

  • 17-04-2009 7:57am
    #1
    Nappy
    Registered Users, Registered Users 2 Posts: 329 ✭✭


    Draw 4 cards from a standard deck. What is probability that all 4 cards are different values given

    (i) the four suits are different?

    (ii) we drew 2 spades and 2 hearts?

    I cant seem to get this out, I know its conditional probability and ive used formulae but cant get it?
    Can anyone help? I keep getting around .69, but answer is .6008 and .7051


Comments

  • #2
    Mellor
    Registered Users, Registered Users 2 Posts: 39,901 ✭✭✭✭Mellor


    Nappy wrote: »
    Draw 4 cards from a standard deck. What is probability that all 4 cards are different values given

    (i) the four suits are different?
    Given that the four suits are the different, each card has a decreasing chance of matching a previous card, The first being 13/13, the next being 12/13 etc
    So;

    13/13*12/13*11/13*10/13

    Which equals .6008
    (ii) we drew 2 spades and 2 hearts?
    Now the two spades and two hearts never match, so here its just the chance of the hearts matching the spades.

    So the chance of the first spade not matching is 11/13 and the second is 10/12

    11/13*10/12=.7051


  • #3
    mark renton
    Closed Accounts Posts: 2,696 ✭✭✭mark renton


    Hey Mellor - have you any links to poker algorithms?


  • #4
    Mellor
    Registered Users, Registered Users 2 Posts: 39,901 ✭✭✭✭Mellor


    john47832 wrote: »
    Hey Mellor - have you any links to poker algorithms?

    Theres plenty of monte carlo sims out there, and icm ones too, but these are generally fill in the blanks and press the button,

    As for playing algorithms, all thats needed is a random number generator that accounts for previous numbers (on the same deal). Its common for poker hands will have to to 45 cards dealt. 52 is also possible.

    They are good for an answer but there is no working out involved, I do most of my poker sums on paper. The closed nature of a de4ck means that even the most complicated calc just takes a bit of time to map out


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