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The First Lady (Posted on 2024-01-30) Difficulty: 2 of 5
A standard deck of 52 cards contains, inter alia, four Queens.
After a perfect shuffle, one turns cards from the top one after another, until the first Queen appears.

Please provide your justified estimate at what step will the 1st Queen appear.

No Solution Yet Submitted by Ady TZIDON    
Rating: 5.0000 (2 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
re(2): Excel (spoiler) Comment 12 of 12 |
(In reply to re: Excel (spoiler) by Brian Smith)

I like your reasoning, but I don't think you should round to the nearest whole card.  It's ok for expected value to not be an integer.  Note: 11th is not the most likely position of the first card.  


I looked at a smaller case: 6 cards of which 3 are queens.

1st Q, count
1 10
2 6
3 3
4 1

Giving a mean (expected) first queen at 35/20 = 7/4 (in agreement with your formula)
a median of 1.5 (half the time less than 1.5, half the time more)
most likely first queen = 1

  Posted by Jer on 2024-01-31 13:04:38
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