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**mom****Member**- Registered: 2012-04-25
- Posts: 94

what is the probability of getting either a black card or an ace in one draw from an ordinary deck of 52 cards?

I got 8/13

26/52 black cards + 4/52 aces=8/13

the answer that was marked correct is 7/13

What did I do wrong?

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 104,162

( 6 / 13 ) + ( 1 / 13 ) = ( 7 / 13 )

Can you see why?

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.** **A number by itself is useful, but it is far more useful to know how accurate or certain that number is.**

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**OzMark****Member**- Registered: 2013-06-10
- Posts: 9

There are

13 black spades (including the ace of spades),

13 black clubs (including the ace of clubs),

the ace of diamonds,

the ace of hearts,

= 13 + 13 + 1 + 1 =28

28/52 = 7/13

Thanks

*Last edited by OzMark (2013-06-12 01:10:28)*

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