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Doubling confusion

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03-09-2015 , 08:48 AM

Kamba

enthusiast

Join Date: Feb 2015 Posts: 93

Hello All. This is my first post, so hope all works!
I got into this position against GNU today.
Black on roll. Apparently this is a redouble take. With only 19 rolls that win me the game and the rest that lose it, I can't understand the redouble at only 53% to win?

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03-09-2015 , 09:15 AM

Robertie

old hand

Join Date: May 2004 Posts: 1,954

The short answer: If there's one roll left in the game and you're a favorite, you should double. Whatever you rate to win with the cube on 8 will be doubled with the cube on 16.

The actually calculation looks like this. Say you're playing for $10/point. If you don't double you win $80 53% of the time and lose $80 47% of the time.

So $80*0.53 - $80*0.47 = $80*0.06 = +$4.80.

If you double to 16 and he takes, substitute $160 for $80 above and you get a profit of

$160*0.06 = $9.60.

If you know all this intellectually but don't want to double because you don't want to lose $160 sometimes, you're playing for stakes that are too high.

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03-09-2015 , 09:47 AM

Kamba

enthusiast

Join Date: Feb 2015 Posts: 93

Oh boy. That should have been immediately apparent! Many thanks for the answer.

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03-09-2015 , 11:27 AM

peachpie

centurion

Join Date: Aug 2014 Posts: 182

You are right that 53% to win is normally not enough to double. Last roll situations are a special case though: you can't ever be redoubled, and are 100% to lose your market. So, you should double on any advantage at all.

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If you know all this intellectually but don't want to double because you don't want to lose $160 sometimes, you're playing for stakes that are too high.

Same is true for red if he passes, although that would be a much greater error.

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