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Mathematics 9 Online
OpenStudy (anonymous):

HELP!!!!! If 6 cards are drawn at random from a standard deck of 52 cards, what is the probability that exactly 2 of the cards are spades?

OpenStudy (anonymous):

there are 26 spades 2/26

OpenStudy (anonymous):

7.69 but thats not one of my answers so Im doing something wrong

OpenStudy (sidsiddhartha):

There are 13 spades out of 52 cards total. so what is the prob of drawing a spade on a first draw ?

OpenStudy (anonymous):

oh I dont know why I was saying 26 13/52

OpenStudy (anonymous):

25%

OpenStudy (anonymous):

No.of ways drawing 6 cards out of 52 = 52C6 = 52!/(6!)*(46!) No.of ways to select 2 spades = 13C2 =13!(11!)*2!

OpenStudy (anonymous):

Now calculate the prob can u?

OpenStudy (sidsiddhartha):

its just 13/52 now there are total 51 cards and 12 spades so So P(drawing spade on second draw) = 12/51 just keep on going like this till the 6 card is drawn

OpenStudy (anonymous):

prob = (39C4*13C2)/(52C6)

OpenStudy (anonymous):

39/4

OpenStudy (anonymous):

sry binks i went some where wrong

OpenStudy (anonymous):

13/52 12/51 11/50 10/49 9/48 8/47 @sidsiddhartha

OpenStudy (anonymous):

@Muser can u help me?

OpenStudy (anonymous):

P(drawing spade on first draw) = 13/52 I need to find out after drawing 6 cards the probability of drawing 2 spades

OpenStudy (anonymous):

No, sorry. I was trying to work it out but I am definitely doing it incorrectly.

OpenStudy (anonymous):

ok thanks

OpenStudy (anonymous):

@amistre64 can u help please

OpenStudy (anonymous):

@eliassaab can u help please???

OpenStudy (anonymous):

(13/52)(8/47) ??? 2/47 = 0.0426 still not right

OpenStudy (anonymous):

@texaschic101 please help!!!

OpenStudy (amistre64):

If 6 cards are drawn at random from a standard deck of 52 cards, what is the probability that exactly 2 of the cards are spades? 13*12*(52-13)*(52-14)*(52-15)*(52-16) ------------------------------------ 52*51* 50* 49* 48* 47 but im sure thats not 100% accurate.

OpenStudy (amistre64):

13 cards are spades, 39 are not spades ss s's's's' (6 2) = 15 ways to arrange those? 1 5 10 1 6 15 (6 2) = 15 ways to arrange those

OpenStudy (anonymous):

now im confused

OpenStudy (amistre64):

13C2 * 39C4 ------------ 52C6

OpenStudy (amistre64):

or 13P2 * 39P4 15 * ----------- 52P6

OpenStudy (anonymous):

thanks now i see how to write it out

OpenStudy (amistre64):

i believe this is called a hypergeometric probability distribution but terminology never was a strong suit

OpenStudy (anonymous):

i get the answer but still trying to figure out steps

OpenStudy (amistre64):

consider, there are 39 cards that are NOT spades, there are 39*38*37*36 ways to pick 4 of them out of the deck there are 13 cards that ARE spades, there are 13*12 ways to pick 2 of them out of the deck. since this is without replacement, the number of cards in a deck reduce by 52*51*50*49*48*47; -1 card for each pull there are 15 different ways to sort the pulls

OpenStudy (anonymous):

thanks so much hope I can remember this lol

OpenStudy (amistre64):

we had to determine the prob of poker hands last term .... it was horrible!! :)

OpenStudy (anonymous):

i get the concept though

OpenStudy (anonymous):

:)

OpenStudy (anonymous):

hi

OpenStudy (anonymous):

so whats the answer?

OpenStudy (anonymous):

0.315 I believe

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