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: 105,303

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.
No great discovery was ever made without a bold guess.

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