Three cards are drawn successively without replacement from a well-shuffled standard…

MATHEMATICS · Multi-part · A Level · Mathematics · Probability · Probability

Problem

Three cards are drawn successively without replacement from a well-shuffled standard deck of 5252 cards. Let E1E_1 be the event that the first card drawn is red, E2E_2 the event that the second card drawn is an ace, and E3E_3 the event that the third card drawn is a king. The joint probability P(E1∩E2∩E3)P(E_1\cap E_2\cap E_3) is known to be 12210\dfrac{1}{2210}. (i) Express P(E1∩E2∩E3)P(E_1\cap E_2\cap E_3) in terms of P(E1)P(E_1), P(E2∣E1)P(E_2\mid E_1) and P(E3∣E1∩E2)P(E_3\mid E_1\cap E_2). Hence calculate the value of P(E3∣E1∩E2)P(E_3\mid E_1\cap E_2). (ii) Compute the unconditional probability that the third card is a king after any two cards have been removed from the deck. Compare this probability with the value obtained in part (i) and comment on whether the events involved are independent.

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