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# S2 practice question help watch

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

Thanks
2. where did you get this question? this best not be in todays paper
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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Updated: June 23, 2004
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