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#1 2013-06-11 08:07:10

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

card probability

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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#2 2013-06-11 08:14:59

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: card probability

( 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.
Always satisfy the Prime Directive of getting the right answer above all else.

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#3 2013-06-11 12:28:55

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

Re: card probability

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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