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Probability of getting 3 Blackjacks in a row?

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January 13th, 2011 at 2:47:56 PM permalink
L8lori
Member since: Jan 13, 2011
Threads: 1
Posts: 1
Wizard,

You have an awesome sight & I have enjoyed your articles for a few years now... thank you for giving us this web site.

I am been running different numbers thru my head trying to come up with a way to compute the probabilities of getting 3 blackjacks in a row with a 6 deck continuous shuffle machine? Or even the odds of getting 5 blackjacks in a row with the same situation?

Also... I saw a casino promotion where you got a drawing ticket every time you were dealt a red queen and a black ace... is there a way to calculate my odds of getting this type of hand in blackjack?

Thank you
L8lori
January 13th, 2011 at 3:40:53 PM permalink
HKrandom
Member since: Oct 1, 2010
Threads: 16
Posts: 126
Odds of getting a blackjack are roughly 4/13*1/13*2 so the chances of that happening 3 times in a row are about 1 in 10,000 and the chances of getting 5 in a row are about 1 in 4,200,000. The chance of getting a red queen and a black ace is 2*2/52*2/52 or 1/338.
January 13th, 2011 at 4:17:14 PM permalink
Ayecarumba
Member since: Nov 17, 2009
Threads: 113
Posts: 2047
From the Wizard of Odds Blackjack page, the probability of getting a blackjack on a six deck game is: 0.047489. The probability of this happening three times in a row is: (.047489)^3 = .00010709743 or 1 in 9,337

Edit: FYI, from the Wizard's Blackjack page, the general formula for calculating the odds of a blackjack in n decks is: 2*(4/13)*(4n/(52n-1)).
January 13th, 2011 at 4:28:58 PM permalink
mkl654321
Member since: Aug 8, 2010
Threads: 65
Posts: 3412
Quote: Ayecarumba
From the Wizard of Odds Blackjack page, the probability of getting a blackjack on a six deck game is: 0.047489. The probability of this happening three times in a row is: (.047489)^3 = .00010709743 or 1 in 9,337


I'm glad it's that low, because I ever actually got three blackjacks in a row, the earth would open up and swallow me and the casino.
The fact that a believer is happier than a skeptic is no more to the point than the fact that a drunken man is happier than a sober one. The happiness of credulity is a cheap and dangerous quality.---George Bernard Shaw
January 13th, 2011 at 4:31:01 PM permalink
ElectricDreams
Member since: Sep 8, 2010
Threads: 4
Posts: 194
Quote: mkl654321
I'm glad it's that low, because I ever actually got three blackjacks in a row, the earth would open up and swallow me and the casino.


I got two in a row a few days ago. I was all like "yay! Blackjack again!"

I think I colored up after that, because I wanted to leave on a high point ;-)
January 13th, 2011 at 4:59:59 PM permalink
Ayecarumba
Member since: Nov 17, 2009
Threads: 113
Posts: 2047
Quote: L8lori
I saw a casino promotion where you got a drawing ticket every time you were dealt a red queen and a black ace... is there a way to calculate my odds of getting this type of hand in blackjack?


In a six deck shoe (or CSM) there are 12 red queens and 12 black aces. The odds of getting dealt one of each is (12/312)*(12/311) = .001484 or 1-in-674.
January 13th, 2011 at 5:20:30 PM permalink
Ayecarumba
Member since: Nov 17, 2009
Threads: 113
Posts: 2047
Quote: mkl654321
I'm glad it's that low, because I ever actually got three blackjacks in a row, the earth would open up and swallow me and the casino.


1-in-9,337 is not that unusual, when, according to the Wizard, the odds of getting a royal flush in VP, if all you did was try to get a Royal every draw are 1-in-23,081.
January 13th, 2011 at 5:44:29 PM permalink
PapaChubby
Member since: Mar 29, 2010
Threads: 9
Posts: 342
Quote: Ayecarumba
In a six deck shoe (or CSM) there are 12 red queens and 12 black aces. The odds of getting dealt one of each is (12/312)*(12/311) = .001484 or 1-in-674.


You neglected that the cards may be dealt in either order, so the probability is twice as great as you calculated.
January 13th, 2011 at 5:45:19 PM permalink
PapaChubby
Member since: Mar 29, 2010
Threads: 9
Posts: 342
I don't think I have ever been dealt three blackjacks in a row, but I'm sure I've seen the dealer get 'em on several occasions. Sometimes the math just doesn't tell the whole story.
January 13th, 2011 at 6:22:59 PM permalink
Ayecarumba
Member since: Nov 17, 2009
Threads: 113
Posts: 2047
Quote: PapaChubby
You neglected that the cards may be dealt in either order, so the probability is twice as great as you calculated.


Thank you for the correction PapaChubby. This is my calculation: (24 (12 red Q's and 12 black A's) / 312 total cards in six decks) * (12 red Q's or black A's, depending on what was dealt first/311) = 1-in-337
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