Math Is Fun Forum
  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

#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?

Offline

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

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 84,363

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.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Offline

#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)

Offline

Board footer

Powered by FluxBB