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pokerdav
21 Dec 09 20:36
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Date Joined: 17 Jul 02
| Topic/replies: 17 | Blogger: pokerdav's blog
A die is rolled 6 times. What are the probabilities that there are:

a) mostly odd numbers
b) mostly even numbers
c) 3 of each
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Report DStyle December 21, 2009 8:46 PM GMT
34.4%
34.4%
31.2%
Report mande December 21, 2009 9:01 PM GMT
a) 34.375 %
b) 34.375 %
c) 31.25 %
Report mande December 21, 2009 9:02 PM GMT
slow countin :D
Report pokerdav December 21, 2009 9:02 PM GMT
im sure you're right, but how do you work it out please?
Report Zola's Back Heel December 21, 2009 9:04 PM GMT
with maths.
Report [x] These checkboxes suck December 21, 2009 9:07 PM GMT
a) = (6C4 + 6C5 + 6C6)/(2^6)
= (15 + 6 + 1)/64
= 22/64 = 11/32

b) P(odd) = P(even) therefore the answer is the same (11/32)

c) P(3 of each) = 1 - a) - b)
= 1 - 22/32
= 10/32
= 5/16
Report DStyle December 21, 2009 9:09 PM GMT
the probability of any combination of odd and even numbers over 6 throws is 1/64 or

(1/2)^6, i.e. 6 consecutive throws of a dice with the outcome being a 50/50 chance (odd/even)

you need to then know or work out the binomial coefficients for the different outcomes:

there are 20 different ways you can organise 3 even and 3 odd numbers over 6 throws, so the probability of getting 3 even and 3 odd is 20/64

you can work out the other two answers from here on the basis that the remaining probability represents either "mostly" situation, and that the chance of more odd numbers and the chance of more even numbers is equal so 22/64 each.

alternatively you can use the other binomial coefficients (6 odd numbers - 1, 5 odd numbers - 6, 4 odd numbers -15): 1+6+15 = 22.
Report pokerdav December 21, 2009 9:12 PM GMT
was struggling to get my head round it. many thanks
Report Lori December 21, 2009 9:37 PM GMT
Let us know what mark you get.
Report History Maker December 22, 2009 10:26 AM GMT
Zola's Back Heel 21 Dec 22:04


with maths.


Made me laugh.
Report zipper December 22, 2009 10:50 AM GMT
34.4, .. 34.4 .. 31. 2.. is correct .. why it adds upto 100%
Report zipper December 22, 2009 10:54 AM GMT
Mande your odds add up to ...101%
Report zipper December 22, 2009 10:57 AM GMT
You cannot have more than 100% of anything ..... 100% means you got the lot .
Report Mr Ed December 22, 2009 11:21 AM GMT
a) 34.375 %
b) 34.375 %
c) 31.25 %

total 100%
Report zipper December 22, 2009 11:25 AM GMT
Mr Ed lets not split hairs whats your nap today ......
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