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Discussion Response Post to: HEAD AND TAIL

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Bipin Dubey (13679)

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Probability of choosing the biased coin = 1/(n+1)
Probability of coming head on tossing biased coin = 1

Probability of choosing fair coin = n/(n+1)
Probability of coming head on tossing fair coin = 1/2

Hence probability of coming head = 1/(n+1) + [n/(n+1)].[1/2] = (n+2)/(2n+2)

Given this is equal to 7/12.
Hence (n+2)/(2n+2) = 7/12

Gives n = 5.

Best Wishes

Bipin Kumar Dubey Chemical Dept. IIT Kharagpur

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