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# Probability

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Intern
Joined: 12 Aug 2017
Posts: 1

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23 Aug 2017, 09:30
Two cards are drawn at random from pack of 52 cards , what's the probability that either both are black or both are queens?

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Intern
Joined: 10 Dec 2015
Posts: 36
Location: India
Concentration: Strategy, Finance
Schools: Rotman '21
GMAT 1: 680 Q48 V36
GPA: 3.3

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23 Aug 2017, 09:48
We have n(s) = 52C2= 1326.
Let A = event of getting both black cards
B = event of getting both queens
A∩B = event of getting queen of black cards
n(A) = 26C2 = 325, n(B)= 4C2 = 6 and n(A∩B) = 2C2 = 1
P(A) = n(A)/n(S) = 325/1326;
P(B) = n(B)/n(S) = 6/1326 and
P(A∩B) = n(A∩B)/n(S) = 1/1326
P(A∪B) = P(A) + P(B) - P(A∩B) = 55/221
Manager
Joined: 22 May 2015
Posts: 108

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23 Aug 2017, 09:49
1
Drawing simultaneously or one after another without replacement?

If drawing simultaneously it is 55/221 .
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Senior PS Moderator
Joined: 26 Feb 2016
Posts: 3386
Location: India
GPA: 3.12

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23 Aug 2017, 10:29
sachchidanand wrote:
Two cards are drawn at random from pack of 52 cards , what's the probability that either both are black or both are queens?

Sent from my iPhone using GMAT Club Forum mobile app

Kindly follow the rules before posting.

This question has already been discussed here : 2-cards-are-drawn-at-random-106543.html

--== Message from the GMAT Club Team ==--

THERE IS LIKELY A BETTER DISCUSSION OF THIS EXACT QUESTION.
This discussion does not meet community quality standards. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.

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Re: Probability   [#permalink] 23 Aug 2017, 10:29
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