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

It is currently 31 Jul 2014, 09:48

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

this will probably be fairly easy for some of you, but i'm

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Intern
Intern
User avatar
Joined: 28 May 2003
Posts: 13
Followers: 0

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

this will probably be fairly easy for some of you, but i'm [#permalink] New post 26 Jul 2004, 11:03
this will probably be fairly easy for some of you, but i'm stuck on it:

a fair coin with sides marked heads and tails is to be tossed eight times. what is the probability that the coin will land tails side up more than five times?
Manager
Manager
User avatar
Joined: 19 Jul 2004
Posts: 75
Followers: 1

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

 [#permalink] New post 26 Jul 2004, 11:18
We would have to use the bernoullis theorem....

P=nPk+nP(k+1)+.....nPn

where nPk=nCk*(p^k)*((1-p)^(n-k))....sounds simple and fair enuff :rocket

Lets calculate....
_________________

To Strive, To Seek and Not to Yield

Intern
Intern
User avatar
Joined: 28 May 2003
Posts: 13
Followers: 0

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

 [#permalink] New post 26 Jul 2004, 11:27
Karthik wrote:
We would have to use the bernoullis theorem....

P=nPk+nP(k+1)+.....nPn

where nPk=nCk*(p^k)*((1-p)^(n-k))....sounds simple and fair enuff :rocket

Lets calculate....


ah, i c. thanks, this helps a lot.
Manager
Manager
User avatar
Joined: 19 Jul 2004
Posts: 75
Followers: 1

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

 [#permalink] New post 26 Jul 2004, 12:06
ian,

is there any easy way of handling this....calculating the probability in this case is cumbersome...is this a GMAT Type anyway??
_________________

To Strive, To Seek and Not to Yield

CEO
CEO
avatar
Joined: 15 Aug 2003
Posts: 3470
Followers: 59

Kudos [?]: 659 [0], given: 781

 [#permalink] New post 26 Jul 2004, 13:24
IMO, formulas are good, but not good enough. do try to understand why the formula works the way it works. ETS makes a living out of making simple problems look difficult. If just one thing is out of place, it wouldnt be difficult to panic.

Search for explanations by anupag/akamai brah/stolyar for this.

Thanks
Praetorian
Manager
Manager
avatar
Joined: 16 May 2004
Posts: 65
Location: columbus
Followers: 1

Kudos [?]: 4 [0], given: 0

 [#permalink] New post 26 Jul 2004, 18:30
so is the final ans (1/2)^8 ( 8C5 + 8C6 + 8C7 + 8C8)
= 93/256
Joined: 31 Dec 1969
Location: United States
Concentration: Marketing, Other
GMAT 1: 710 Q49 V38
GMAT 2: 660 Q V
GPA: 3.64
WE: Accounting (Accounting)
Followers: 0

Kudos [?]: 51 [0], given: 75166

 [#permalink] New post 26 Jul 2004, 21:49
Way to approach the problem is as follows:

1. Total no. of outcomes is 2^8. You are flipping 8 times and probability of tail showing up everytime you flip the coin is 1/2. When you do it eight times it is 1/2^8. Or the total outcomes (denominator) is 2^8.

2. Now, the question is what is the probability of tails coming up atleast 5 times - this means that tails can appear 5 times, 6 times, 7 times or all the 8 times. Think combinations and you'll get 8C5 + 8C6 + 8C7 + 8C8 ways of getting atleast 5 tails and this adds up to 93.

3. The answer would be 93/2^8 = 93/256.
Director
Director
User avatar
Joined: 16 Jun 2004
Posts: 893
Followers: 1

Kudos [?]: 9 [0], given: 0

GMAT Tests User
 [#permalink] New post 26 Jul 2004, 22:41
Sorry did not log in last time. the guest was me.
CIO
CIO
User avatar
Joined: 09 Mar 2003
Posts: 466
Followers: 1

Kudos [?]: 24 [0], given: 0

GMAT Tests User
 [#permalink] New post 27 Jul 2004, 05:41
Karthik wrote:
ian,

is there any easy way of handling this....calculating the probability in this case is cumbersome...is this a GMAT Type anyway??


I agree with smandalika and venksune on this one. However, the question asks for the "probability that the coin will land tails side up more than five times". I don't think that includes 5 times, so I only did it with 6, 7, and 8 times. My answer: 37/256.
Manager
Manager
avatar
Joined: 16 May 2004
Posts: 65
Location: columbus
Followers: 1

Kudos [?]: 4 [0], given: 0

 [#permalink] New post 27 Jul 2004, 19:44
good catch Ian. I somehow missed that one

regards

smandalika
Director
Director
User avatar
Joined: 16 Jun 2004
Posts: 893
Followers: 1

Kudos [?]: 9 [0], given: 0

GMAT Tests User
 [#permalink] New post 27 Jul 2004, 22:21
Ian is right. Should be 37/256. :oops
Intern
Intern
User avatar
Joined: 28 May 2003
Posts: 13
Followers: 0

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

 [#permalink] New post 28 Jul 2004, 13:02
ian7777 wrote:
Karthik wrote:
ian,

is there any easy way of handling this....calculating the probability in this case is cumbersome...is this a GMAT Type anyway??


I agree with smandalika and venksune on this one. However, the question asks for the "probability that the coin will land tails side up more than five times". I don't think that includes 5 times, so I only did it with 6, 7, and 8 times. My answer: 37/256.


indeed, 37/256 is the OA.
  [#permalink] 28 Jul 2004, 13:02
    Similar topics Author Replies Last post
Similar
Topics:
1 Experts publish their posts in the topic Easy One... But some how I'm confused onedayill 5 04 Jul 2010, 07:47
Here are two GMAT Prep questions that are fairly easy, but bz9 10 24 Feb 2007, 20:36
This one should be fairly easy for many of you. I guessed it uvs_mba 6 06 Nov 2006, 06:37
Ok, I'm probably going to be embarassed by how easy this is, uphillclimb 3 13 Sep 2006, 07:31
This is a fairly easy one, but ... The price of lunch for wlee76 1 07 Jul 2006, 17:06
Display posts from previous: Sort by

this will probably be fairly easy for some of you, but i'm

  Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Privacy Policy| 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®.