Yahoo Answers: Answers and Comments for Math: Probability, please help. (Chance of something happening if you do it twice.)? [Mathematics]
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From hiatuslucari
enUS
Sat, 14 Feb 2009 20:59:04 +0000
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Yahoo Answers: Answers and Comments for Math: Probability, please help. (Chance of something happening if you do it twice.)? [Mathematics]
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From nickname: For these sort of questions it is easier if yo...
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Sat, 14 Feb 2009 21:20:11 +0000
For these sort of questions it is easier if you put the question the other way around : 'roll two dice, what will the chance of neither having a six'.
For one die the chance is 5/6 of not getting a six. Therefore for two dice the chance is 5/6 x 5/6 = 25/36 of not getting a six. Therefore the chance of getting at least one six from 2 dice is 1  25/36 = 11/36.
Then extending this to the chance of no sixes from two throws of two dice  this would be 25/36 x 25/36. Therefore the chance of getting at least one six on two throws is 1  25/36 x 25/36  approx 0.5
Rolling the two dice six times:
prob(6) = 1  (25/36)^6  approx 0.88

From four_to_the_fourth_power: If you only want at least one 6, you are reall...
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Sat, 14 Feb 2009 21:15:22 +0000
If you only want at least one 6, you are really looking for the complement of the chance that you roll twice and don't get a 6.
There is a 5/6 chance that you don't get a 6 on any one roll. So with two rolls, multiply (this is a basic counting/probability principle) the probabilities of NOT getting a 6 together:
5/6 * 5/6 = 25/36
Again, this is the chance that you roll twice and get two non6s. So the rest of the time, 11/36 times, you will get at least one 6.
You should only add the probabilities if you want to know the chances of, say, rolling a 6 or a 5 on one roll. Whenever you are dealing with multiple, independent events, you need to multiply probabilities together to find the probability of both things happening. For example, the chances of both dice landing on 6 are 1/6 * 1/6 = 1/36.

From shreve: Chance Of Something Happening
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Thu, 02 Mar 2017 10:32:26 +0000
Chance Of Something Happening