I'm interested in learning about the probability and rationale of poker?

Question

What is the probability of getting a "21" (i think it's also called blackjack) from a fair deck? And how would you find that?

Answer 1

Well blackjack and poker are 2 different games entirely.  As far as figuring out the odds of getting a specific hand you just need to look at the cards and their probabilities.  This isn't exact but it will give you an idea of how these things are figured out.

You're going to need an ace and a KQJorT.  So in card 1 you need AKQJT.  That's 5 out of 13.  For each card it's approximately 0.0769.  If you get a KQJT then you need an ace next so for that to happen with each card is 0.0769*0.0769 or 0.0059.  There's 4 of them so we multiply by 4 and get 0.024.  Then there's the ace which is 0.0769 and we have 4 cards that will help you on the second so we add 0.0769 4 times (0.3076)and multiply by the ace odds (0.0769) and get 0.024.  So we add that with the other 0.024 and get 0.048 which is about 1 in 20.  

A.J.

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