Submitted 7 hours ago by Yermaw@lemm.ee to [deleted]
Its 1/6 to roll a 7 with two 6-sided dice. You can get weighted dice that make it more likely to land on a certain number.
Does having one weighted dice change the odds at all? My gut says no but reality is a tricky bitch and I’m convinced im wrong somehow.
You’re marginally less likely to roll a 7 with a single weighted die.
My reasoning: if you use your weighted die, whoever you’re gambling against might figure it out. Now they’re pissed, they’re gonna give you the beat down. But you’re packing, and OH SHIT YOU DIDN’T MEAN TO HIT HIM IN THE HEAD YOU WERE AIMING FOR HIS LEG SHIT SHIT and now you’re serving jail time for manslaughter and dice aren’t allowed in jail, thus you won’t be able to roll any 7s for a while.
Don’t worry, there are dice in (at least some) prisons, every cell block had at least one D&D group going with 4-6 people, and they used dice.
Source: Was a prison guard in the ARMY for 4 years at Fort Lewis.
Ah, so the chance of rolling a 7 changes to 1/20?
I read an article written by an inmate who explained how they’d form dice out of toilet paper (because dice were banned in his case) to play D&D. I assumed that was the case in most facilities.
You had me in the first half for real
There is statistically no difference if one is weighted because it’s gone from 6/36 to 1/6.
Your question is already answered correctly, so I’m just chiming in with thoughts on a similar situation :)
If you weigh both dice, it gets interesting again.
The obvious is to make one die roll always 3 and the other always 4, and get 1/1 chance of 7 but that’s boring and you’ll only get a few throws in before you’re obviously cheating.
Dice are arranged so that opposite sides always add up to 7, meaning you can get 1,2,3 around one corner and 4,5,6 around the opposite corner. So if you weigh opposite corners on each die, you get a 1/3 chance of rolling a 7 by varying combinatons. You might get away with a few more rolls like that.
If a die is weighted, the first roll is no longer 1/6 probability to get a 7; the roll isn’t random and there isn’t enough info. I think though it’s 3/12 (1/4 for a 7 (6+1, 5+2, 4+3)?
You need to roll two dice to get a sum of seven. Consider two fair dice: No matter what the first dice lands on, there’s a 1/6 probability that the second dice lands on the number you need to get a total of seven.
Consider now that one dice is weighted such that it always lands on 6. After you’ve thrown this dice, you throw the second dice, which has a 1/6 chance of landing on 1, so the probability of getting seven is still 1/6.
Of course, the order of the dice being thrown is irrelevant, and the same argument holds no matter how the first dice is weighted. Essentially, the probability of getting seven total is unaffected by the “first” dice, so it’s 1/6 no matter what.
That’s if it’s perfectly weighted. If it’s weighted to roll a 6, it might not always land on 6. This would lower the chance of rolling a 7 depending on what the overall probability profile is on the weighted die.
If a die is weighted, the first roll is no longer 1/6 probability to get a 7
Yes, actually, it is. No matter what the first die lands on, there is a 1 in 6 chance that the second die will land on the corresponding value necessary for a “7”. You could glue the first die to the table with “6” (or any other number) showing, and there will be a 1 in 6 chance that the second die will bring the sum to 7.
Tell me the weights and I told you the probability of getting 7.
At the moment you have P(x) = {X=1 : 1/6, X=2: 1/6…X=6: 1/6). Give me the new P(X) and I calculate this for you.
dhork@lemmy.world 7 hours ago
If your goal is to roll a 7, then no, weighting one die doesn’t help, because it doesn’t matter which side comes up in the weighted die.
(Another way to look at it is that you can place 1 die on whatever side you like, then roll the 2nd die: you still have a 1/6 chance of rolling a combined 7).
However that is only the case for a 7, because you can roll a 7 with any combination of the first die. If your goal is to roll a 12, then weighting one die towards 6 will affect the odds, because you need a 6 on that first die to roll a 12; any other outcome makes it impossible.
hddsx@lemmy.ca 6 hours ago
I mean you can get dice weighted differently so you almost always get a 6 and a 1 for example.
There’s no point in weighing one die. The odds are the same as not weighing any die