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Wilbrham
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#1
Report Thread starter 15 years ago
#1
Can someone please help me with this question

A six-sided die is biased. When the die is thrown the number 5 is twice as likely to appear as any other number. All other faces are equally likely to appear. The die is thrown repeatedly.

Find the probability that

i) the first 5 will occur on the sixth throw,

ii) in the first eight throws there will be exactly three 5's


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S1M
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#2
Report 15 years ago
#2
where did you get this question? this best not be in todays paper :eek:
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wonderboy
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#3
Report 15 years ago
#3
It is off last years...

p(x=5)= 2/7
p(x not = 5)= 5/7

i)
p(x on 6th throw) = (2/7)*(5/7)^5

ii)
p(3 5s in 8 throws) = 8C3*(2/7)^3*(5/7)^5

This is how I done it anyways
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