Mary and John roll seven fair, standard dice (like those seen above). If all rolls are the same, Mary wins. If all rolls are different, John wins. They keep rolling all of the dice until someone wins. Who is more likely to win?
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Ahhh!! Thats Brilliant! I feel like a fool now :P
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me too
But the question doesn't mention how many tries they take.
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trials doesn't matter you indefinitely John will never win
Number of trials is trivial here.
its a game-theory question... they have infinite tries/throws.
it is not dependent on how many tries they will take in 7 dice at last one number will come twice if we take that each die shows a different number
you're all smarter than i am
Ditto!!
yes Pola Forest is Perfectly right seven dice having six side can never show seven seven different number.
Pola is absolutely right. There is no possibility of John winning because of the fact that dice has six sides. and even if john gets different sides the seventh in all cases will have one similar side surely.
that's perfect problem and perfect solution
I wanna kill myself.
exactly........the pigeonhole principle is as mathematical it gets.........if u dont want to rely on pure logic....
I was contemplating on choosing not enough info but then i said since only mary can win, mary is the only one sure to win. Eventually she would.
Number of rolls needs to be clarified. If the game allows only finite rolls, Mary MAY, but not SURELY, win. If infinite rolls are allowed, Mary will surely win. This is a required piece of information to answer the question. As it is stated above, the answer ought to be "Not enough information"...
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yah...
even if finite rolls are there, probability of Mary winning is greater than zero. we have to find probability.
yes thank u
great!unexpected explaination
figured it out... only when calculating --__--'
Its interesting ... if someone uses the complex ideas of probability and reply that there is no enough information.
Common sense, without doing any math, .0.000000001 probability will win against 0 probability
would u tell me what will be the ans if no of dices are 6
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With 6 dice, they could all land differently in 6! ways. They could all be the same in 6 ways.
John will never win because dice only have 6 faces and he will win if all 7 dice have different faces, and it doesn't logic for John to win.
But when I read the topic, I just thought that "the same" mean totally "same", i.e. 7 dice are the same :(
damnit
wow
I would like to clarify something. What does it mean to throw the dice differently?
classic
yes it's correct.i think in a foolish manner
Misinterpreted the problem. I thought all of the dice have to me the same -.-
took me 10 seconds, 7 dice but a regular die only has 6 possible outcomes, that means throwing 7 dice will result to at least 2 outcomes among the 7 are the same.
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in 7 dice, 1-1-1-1-1-1-1 or same logic will happen no matter how many tries it takes, but a different numbers will not happen for 7 dices because the most possible is 1-2-3-4-5-6-last one will either one among 1~6.
Shiz. -_-
Hahaha :v thats right..i should have read more carefully
i am a fool
u r a genius
oh, this one is a tricky problem. I didn't get it at first. I can't stop thinking who can win, with the many probabilities. I had learned one thing, use your common sense. hehe.
So true! Trick question!
We are only sure that John will never win. So right answer must be not enough information.
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The question says that they will throw dice until someone wins , which means 1 of them has to win. Since it can't be John, it must be Mary.
Ahhh! I think I didn't get it, because it was written grammatically wrong! It should be: seven dices! not seven dice.
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"seven dice" is correct. "dice" is plural already.
Ambiguous question. How does throwing the different dice differently differ from throwing them similarly?
(Correct/explain why Mary has more chances)
It is pretty obvious that you can't roll 7 different numbers between 1 and 6. Thus it is impossible for Jhon to win. Therefor Mary is bound to win eventually.
wrong question, it says "if ALL dice..."
A dice has only six faces, so how can the seven dices will attain seven different scores??
They can't - and that's why Mary is sure to win eventually.
Yeah I meant the same thing :)
@Chandra Sahu That's the point of the question. This means that John cannot win, and Mary will eventually win. It may take a while though.
This is a tricky one. If there are 7 dices, they can't be all different.
So that means it's impossible for John to win, which means Mary is the one sure to win.
John will never win because in order to win, John must roll all dice showing all different numbers but a regular die only has 6 sides. Therefore, the probability that Mary will win which is 7 / 2 7 9 9 3 6 is higher than the probability that John will win which is 0 .
I think the probability should be 6/279936=1/46656 because Mary will win if and only if the dice show these 6 combinations, which are 1111111, 2222222, 3333333, 4444444, 5555555, 6666666. So, where is another combination?
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You have calculated the probability of Mary winning on her first roll. They are both going to play until on of them wins. Eventually this will be Mary because John cannot win.
but it does not necessarily imply that mary will win
7 different landings are not possible. so, only mary will win.
There are 6 possibilities for each die and there are 7 dice..S all the dice cannot come up differently....So John can never win...So after some time Mary will win...
because if we have 7 dice then it is definite to repeat one number atleast . So marry will win.
why doesn't any1 notice that even though chances of jon's winning are 0, still that doesn't mean that mary would surely win. her chance of winning is still 7/(6^7) because the question doesnot say that if one loses then the other is the winner!! the question could've been correct if it'd asked who would surely lose.
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Somesh Singh, I just say Marry will win. I didn't say what is the chances of winning her. Marry will win because it is definite that Jon will loose(because his winning chance is 0).
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yeah i agree with u on that friend that jon's chance of winnin is 0, but the question doesn't say that if jon loses then mary surely wins; it could also simply be a tie!! until n unless the question specifies that they both try infinitely, it would be completely wrong to say that mary is sure to win!! please try to understand my doubt.
For the people that really need this - I changed the question, so now it says that they can throw it till infinity. I didn't think it was that hard though.
There are seven dice. Therefore, not all of them can be different, and thus Mary wins.
This is a good example of the pigeon hole principle.
Let's say the first six people each rolled something different; the seventh person, whatever he or she rolls, will repeat one of the results that the other six got because a die only has SIX possible outcomes and there are SEVEN people.
So even though Mary's conditions are hard to meet, John's are IMPOSSIBLE.
What was the name of the murderous math book of yours
a dice have only 6 sides so 7 different side is not possible but same 7 sides is possible.so mary is sure to win
How can seven dices show differently if they have only six sides? So Its Impossible for John to win.
Impossible for John to throw the die differently seven times. :D
simple,the dice have six different faces and seven dices cannot be fully different,atleast two shall carry the same no.
There are 7 dice and each has 6 faces so John can never win since at the least two dice will have same value.On the other hand Mary has probability of 1/46656 of getting the same value in all the dice. So Mary has the chances of winning.
Com 7 dados... João não consegue ganhar porque sempre terá um dado igual
Since John gets different nos on dice,but each dice has six only,7th can not be different.With minimum different nos and 7th dice max 6 taken will make it total 27. While mary b can get gigher nos starting from 4,5 & 6. So Mary is sure to win
K.K.GARG,India
Becoz there are six faces in a dice.. so seven different outcomes is not not possible
As there are 7 dice and each dice has only six different faces it is impossible to get different faces at the same time i.e. at least two dice have same faces at the same time.(pigeonhole's principle)
There are only 6 faces on a cube, so to have 7 different number is impossible. marry may be win but john has no probability .
A dice has six faces and hence at max six different outcomes. If there are seven dice, then it is sure that at least two dice will have the same number...
By using Pigeon Hole Principle it is clear that there can't be 7 different outcomes on a six sided dice........... so surely John can't win therefore Mary will win for sure
Mary is the only person who can win the game. John can never win as throwing seven different digits with only six is impossible.
P(all seven dice have same number) = 6/6^7
P(all seven dice have diff number)= 0 because dice have only six faces and for seven dice at least 2 dice have same number on their faces. So all 7 with diff numbers is not possible.
Hence Mary is sure to win.
no matter how many times the dice is thrown at least two dice will show the same good question.
You are expected to look for hidden facts before you start solving the puzzle. I was caught unaware too!
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The point is to read carefully. There are SEVEN dice, and a dice has only 6 sides. Therefore, even thought it will take Mary a long time, she is sure to win, because it's IMPOSSIBLE to throw all the seven dice differently.