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**Ruichan** **5. Cards from an ordinary deck are turned face up one at a time (w/o replacement). Compute the expected number of cards that need to be turned face up in order to obtain 2 aces. **

Captainblack, this was the way you taught me the last time for a question: **Draw 2 cards without replacement from a deck of playing cards. What is the expected number of aces? **

Let random variable x1 = 1 if an ace turns up on the turn, 0 otherwise.

E(x1) = 1/13

Let random variable x2 = 1 if an ace turns up on the 2nd turn, 0 otherwise.

E(x2) = 1/13

E(x1 + x2) = 2/13

Now, instead of # of ace turning up, it's finding the expected number of cards that needed to be turned to obtain 2 aces. Can I use the same way?

Can anyone please advise? Thank you very much