Ronnie1985
Ronnie1985
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July 13th, 2014 at 2:25:31 AM permalink
There is a guy in a local bar who offers a game with 2 6 sided dice. I want to know the odds of the game and if there is a way to win in the long term.

Rules.
Before each roll you have to say 2 numbers between 1 and 6 but different numbers (eg: 1 and 2 but not 1 and 1 etc).

You then roll the 2 dice at the same time. If one of the 2 numbers you selected comes out you lose. (eg: You say 3 and 6 and 2 and 6 come out you lose as 6 appeared.. If 1 and 5 comes out none of your numbers appear so you beat the first roll).

After each roll he will offer you a payout to walk away or you can gamble and try and beat the next roll to increase your payout. If at any time you lose a roll, you lose your initial bet and obviously he will not pay you any money. You can walk at any time after each roll and take the current payout.

Payouts.

Beat 1 roll: Even money
Beat 2 rolls: 3 to 1
Beat 3 rolls: 8 to 1
Beat 4 rolls: 20 to 1
Beat 5 rolls: 40 to 1
Beat 6 rolls: 100 to 1

Example.
I bet $10 and beat the first roll, he will offer me $10 to walk away now. So I make $10 and keep my $10 initial bet. If I walk, game over and done. If I continue I roll again and win, he will offer me $30 dollars plus my bet to walk away now and so on. If at any time I lose a roll, I instantly lose my initial $10 stake and obviously will not be paid any money. It's a nervey game, you bet $10 and have beaten 4 rolls and the offer is 20 to 1 so $200 to walk now. But one more roll and you double to $400. Gamble and double my potential winnings or take?

Anyways, what are the stats to this game. Is it good for him or the player?
drjohnny
drjohnny
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July 13th, 2014 at 3:49:24 AM permalink
Probability of beating 1 roll: (4/6)^-2 = 1 in 2.25
Probability of beating 2 rolls: (4/6)^-4 = 1 in 5.06
Probability of beating 3 rolls: (4/6)^-6 = 1 in 11.39
Probability of beating 4 rolls: (4/6)^-8 = 1 in 25.63
Probability of beating 5 rolls: (4/6)^-10 = 1 in 57.67
Probability of beating 6 rolls: (4/6)^-12 = 1 in 129.75

The payouts get worse if you keep rolling and only a sucker would play.
ksdjdj
ksdjdj
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July 13th, 2014 at 3:58:27 AM permalink
i hope someone else can prove whether what i am saying is right or not, but i still think this is correct
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2/3 of the time you will not get hit on dice (1) and the % of the time that you are not hit on dice (1) you will also not get hit on dice (2) 2/3 of the time,

2/3 x 2/3 = 44.44%

therefore you will not get hit 44.44..% of the time, so the first roll will be a losing roll for the player 55.55..% of the time
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on the first roll there is a -11.111..% player edge but the bet would win 44.44..% of the time, "so you could continue" to roll two if you wanted to

on the second roll there is a -20.98..% player edge and the bet would win 19.75...% of the time, "" to roll three if you wanted to

on the third roll there is a -20.98..% player edge and the bet would win 8.77..% of the time, "" to roll four if you wanted to

i don't think i need to prove it any further, as you can see it will not be possible to reach a positive player edge for roll's 1 to 6
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extra info below:

for the game to have a break-even point

you would have to be offered 5 to 4 on first roll to consider playing that first roll,

you would have to be offered 4.0625 to 1 on the second roll to consider playing to the second roll,

you would have to be offered at least 10.39... to 1 on the third roll to consider playing to the third roll,
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general 'break-even' formula below:

you would have to be offered at least $2.25 to the power of N, if you wanted to play to the 'Nth' roll
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again i am not sure if this response is correct, so wait until someone else proves it(or disproves it), before thinking i gave the correct answer or not
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ksdjdj
ksdjdj
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July 13th, 2014 at 4:08:29 AM permalink
Quote: drjohnny

Probability of beating 1 roll: (4/6)^-2 = 1 in 2.25
Probability of beating 2 rolls: (4/6)^-4 = 1 in 5.06
Probability of beating 3 rolls: (4/6)^-6 = 1 in 11.39
Probability of beating 4 rolls: (4/6)^-8 = 1 in 25.63
Probability of beating 5 rolls: (4/6)^-10 = 1 in 57.67
Probability of beating 6 rolls: (4/6)^-12 = 1 in 129.75

The payouts get worse if you keep rolling and only a sucker would play.



looks like my answer's were right, according to drjohnny, we must have been answering at about the same time, because when i originally clicked on your post and started writing there was no response from anyone showing.

Edit @ 4:40 am

for the bit where you said "If one of the 2 numbers you selected comes out you lose.", i assumed you meant to say "if 1 or both of the 2 numbers you selected comes out you lose", for my original answer ?!?

because, for two numbers to come out there is an 11.11..% chance of that happening,

if what you said was EXACTLY what you meant, then the game would be a player edge game, with an EV of +11.11..% on the first roll

also to cover all bases, if both of the 2 numbers you chose come out is a PUSH, then you would need to go to at least three rolls, before you had a player edge at the odds you stated
Ronnie1985
Ronnie1985
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July 13th, 2014 at 5:00:26 AM permalink
Hello ksdjdj and drjohnny. Thank you for replying, very appreciated.

If you were to select 1 and 2 for example and rolled a 1 and 5, you would lose as 1 appeared. If you rolled a 2 and 3 you lose as 2 has appeared. if you rolled a 11 you lose as one of your numbers has appeared. If you rolled a 1 and 2 you still lose as one of your numbers has appeared. To win, the 2 numbers you have selected MUST NOT appear. So if ONE or MORE of your numbers were to appear, it's a lost roll.
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