Just hit a very rare occurrence...

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Goldeneye
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Just hit a very rare occurrence...

Post by Goldeneye » Mon Nov 17, 2014 8:26 pm

In JRM just now, I was dealt an ankan as a ko player, and when the dora indicator was flipped up, that ankan was immediately a dora ankan.

Wonder what the probability of that happening is - it's probably very rare...

Iapetus
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Re: Just hit a very rare occurrence...

Post by Iapetus » Mon Nov 17, 2014 8:56 pm

The probability can be calculated with simple combinatorics.

There's a total of (136 choose 14) different starting hands. There's 34 different ankans you can get, and (132 choose 10) different sets of the remaining 10 tiles. The chance of the kan hitting the kan dora is 1/33.

(34*(132 choose 10))/(33*(136choose 14)) = 0.0000756..., or about 1 in 13 thousand hands.

Goldeneye
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Re: Just hit a very rare occurrence...

Post by Goldeneye » Tue Dec 02, 2014 10:14 pm

Wouldn't it be (132 choose 9) and (136 choose 13) instead since I was a ko and I got the ankan in my initial 13 tiles before my first draw and if it is, wouldn't it be...

(34*(132 choose 9))/(33*(136choose 13)) = 0.00005403... or about 1 in 18,507 hands as a ko player or am I doing something incorrect here?

Iapetus
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Re: Just hit a very rare occurrence...

Post by Iapetus » Tue Dec 02, 2014 10:45 pm

Yes, that's correct.

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