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Probability

Question
CBSEENMA12033685

Three cards are drawn successively, without replacement from a pack of 52 well shuffled cards. What is the probability that first two cards are kings and the third card drawn is an ace?

Solution
Let K denote the event that the card drawn is king and A be the event that the card drawn is an ace.
Now,                   straight P left parenthesis straight K right parenthesis space equals space 4 over 52
Also,  P(K | K) is the probability of second king with the condition that one king has already been drawn. Now there are three kings in (52 - 1) = 51 cards.
therefore space space space space space space space space space space space straight P left parenthesis straight K vertical line straight K right parenthesis space equals space 3 over 51
Again, P(A | KK) is the probability of third drawn card to be an ace, with the condition that two kings have already been drawn. Now, there arc four aces in remaining 50 cards.
therefore space space space space straight P left parenthesis straight A space vertical line space KK right parenthesis space equals 4 over 50
By multiplication law of probability, we have
                   straight P left parenthesis KKA right parenthesis space equals space straight P left parenthesis straight K right parenthesis space space space space space space straight P left parenthesis straight K vertical line straight K right parenthesis space space straight P left parenthesis straight A vertical line KK right parenthesis
space space space space space space space space space space space space space space space equals space 4 over 52 cross times 3 over 51 cross times 4 over 50 space equals 2 over 5525

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