Gate Exam General Ability

a gambler has 4 coins in her pocket. two are double headed one is doubled tailed and one is normal.the coins can not be distinguished unless one looks at them.
the gambler takes a coin at random,opens her eyes and sees the the upped face of the coin is a head .what is the probability that the lower face is a head?

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It's a conditional probability question

Let's solve it by most simple method. The coins are of type { HH, HH, TT, HT}

so, there are 5 ways of getting head (i.e. H? or ?H) = P(H)
upon them only in 4 cases head appears in the opposite phase.
so, the probability would be = 4/5 = 0.8
9 years agoHelpfull: Yes(1) No(0)

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