Find all School-related info fast with the new School-Specific MBA Forum

It is currently 30 Aug 2016, 08:46
GMAT Club Tests

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Simultaneous Probability

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
Intern
Intern
avatar
Joined: 06 Apr 2012
Posts: 34
Followers: 0

Kudos [?]: 22 [0], given: 47

GMAT ToolKit User Premium Member
Simultaneous Probability [#permalink]

Show Tags

New post 14 Apr 2012, 09:31
Hi - was wondering if anyone could provide guidance to answering the questions below:

1) what is the probability of picking two cards off the top of a deck of cards and getting a pair?

2) what is the probability of getting at least one pair if four fair six sided dice are rolled simultaneously?

Thanks,
Intern
Intern
avatar
Joined: 06 Apr 2012
Posts: 34
Followers: 0

Kudos [?]: 22 [0], given: 47

GMAT ToolKit User Premium Member
Re: Simultaneous Probability [#permalink]

Show Tags

New post 14 Apr 2012, 11:30
randomguy2012 wrote:
1. Define terms.

2. 1/36

1/6*1/6


52 cards with 13 sets of 4 matching cards. If possible please guide me through the solutions (don't just provide an answer), because I am not clear on the thinking behind the answers here, and perhaps a better way to understand how to solve this type of problems.

Question 2 answer is off... Again whether right or wrong is not as important as a step-by-step vision.

Thanks much,
Intern
Intern
avatar
Joined: 27 Oct 2013
Posts: 31
Schools: Erasmus '17
Followers: 0

Kudos [?]: 0 [0], given: 45

CAT Tests
Re: Simultaneous Probability [#permalink]

Show Tags

New post 04 Jul 2016, 05:47
Ans 2: Total possible combination 6^4

combination w/o any pair: 6*5*4*3.

probability of no pair. = 6*5*4*3/6^4

probality of atleast 1 pair: 1- 6*5*4*3/6^4 = 26/36 = 13/18
Expert Post
EMPOWERgmat Instructor
User avatar
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 7214
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: 340 Q170 V170
Followers: 315

Kudos [?]: 2134 [0], given: 161

Re: Simultaneous Probability [#permalink]

Show Tags

New post 04 Jul 2016, 11:58
Hi All,

While this is an old set of posts, the questions themselves are not too difficult to deal with (although you will need to know how probability 'math' works).

1) With a standard deck of cards, there are 4 suits with 13 cards in each suit. The probability of selecting a pair of cards (with the same face value) off the top of a deck of cards can be calculated like this....

The first card could be ANY of the 52 cards, so it doesn't really matter what it is; it's the second card that ultimately matters (it will either match the first card or it won't). Once the first card is flipped over, there are only 3 remaining cards in the deck that match the first card (and there are 51 cards remaining).

(1)(3/51) = 3/51 = 1/17 = the probability that the first two cards are a matching pair.

2) In probability, there are only two possible outcomes - what you "want" and what you "don't want"; the sum of those two outcomes always totals 1. When a probability question uses the phrase "at least", it's often easiest to calculate the probability of NOT getting what you "want" and subtracting that fraction from the number 1. In that way, you'll have the probability of what you DO want.

Here, the wording of the question is a bit vague, but I'm going to interpret it to mean "... the probability of getting at least one duplicate value among the 4 dice rolls..." With this question, I'm going to calculate the probability of not having any duplicates...

The first roll can be any of the 6 possible numbers.

First die: 1
Second die (can't match the first die): 5/6
Third die (can't match either of the first two dice): 4/6
Fourth die (can't match any of the first three dice): 3/6

(1)(5/6)(4/6)(3/6) =
(1)(5/6)(2/3)(1/2) =
10/36 =
5/18 = the probability of NO matching values

1 - 5/18 = 13/18 = the probability of at least one duplicate value

GMAT assassins aren't born, they're made,
Rich
_________________

Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save $75 + GMAT Club Tests

60-point improvement guarantee
www.empowergmat.com/

***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************

Re: Simultaneous Probability   [#permalink] 04 Jul 2016, 11:58
    Similar topics Author Replies Last post
Similar
Topics:
Experts publish their posts in the topic probability ohiovictor 3 26 Jan 2015, 10:04
Experts publish their posts in the topic Probability UlisesOrdonez 1 28 Nov 2013, 15:12
Probability karthik666 0 26 Oct 2013, 04:58
Experts publish their posts in the topic probability question chhandita 3 07 May 2013, 01:59
1 Experts publish their posts in the topic probability question stringworm 3 29 Oct 2011, 22:08
Display posts from previous: Sort by

Simultaneous Probability

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.