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Picking cards (Posted on 2006-08-17) Difficulty: 3 of 5
A player picks random cards from an ordinary card deck, without returning them to the deck. How many cards should he pick so as to get at least one ace with 70% probability?

No Solution Yet Submitted by atheron    
Rating: 3.0000 (1 votes)

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Solution Solution | Comment 5 of 7 |

The first card is drawn with a 1/13 or aprox. 7.69% chance of Ace.

The secound card compound with the first yelds an aprox. 15.53%.

The third an aprox. 23.5%

The fourth an aprox. 31.7%

The fifth an aprox. 40.0%

The sixth an aprox. 48.5%

The seventh an aprox. 57.2%

The eighth an aprox. 66.1%

The nineth an aprox. 75.2% So it would take nine cards

  Posted by Luna on 2006-08-18 17:01:00
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