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Probability question

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by ksh » Thu May 29, 2008 9:24 am
Is it 2*1/2^5=1/16?
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by Carlo75 » Thu May 29, 2008 9:35 am
I think:

The probability to get tails at the first and second tosses is 1/4 (1/2*1/2) - TT
The probability to get heads at the last tree tosses is 1/8 (1/2*1/2*1/2) - HHH
The probability to get TTHHH is 1/4*1/8 = 1/32

the prop to get exactly 2 tails in 5 tosses is 1/32*2C5 = 1/32*(5!/2!*3!) =>1/32 * (5*4/2) = 5/16

but I am in doubt, please could somebody confirm that?
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by aatech » Thu May 29, 2008 9:47 am
These are the possible ways of getting 2 tails

HHHTT, HHTHT, HTHHT, THHHT, THHTH, THTHH, TTHHH = 7 ways

Total ways of getting head or tail = 32

So, prob = 7/32. IMO
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by netigen » Thu May 29, 2008 12:01 pm
total number of cases = 2^5 = 32

number of cases with 2 tails = 5C2 = 5x2 = 10

prob = 10/32 = 5/16
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by egybs » Thu May 29, 2008 3:24 pm
You missed a few:

HTHTH, HTTHH, HHTTH. So total is 10/32 = 5/16
aatech wrote:These are the possible ways of getting 2 tails

HHHTT, HHTHT, HTHHT, THHHT, THHTH, THTHH, TTHHH = 7 ways

Total ways of getting head or tail = 32

So, prob = 7/32. IMO
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by aatech » Fri May 30, 2008 5:38 am
egybs wrote:You missed a few:

HTHTH, HTTHH, HHTTH. So total is 10/32 = 5/16
Thanks...
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