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

It is currently 07 May 2015, 02:04

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

If a coin has an equal probability of landing heads up or

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Intern
Intern
avatar
Joined: 21 Nov 2007
Posts: 11
Followers: 0

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

If a coin has an equal probability of landing heads up or [#permalink] New post 27 Dec 2007, 01:43
6
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

63% (01:55) correct 37% (00:46) wrong based on 250 sessions
If a coin has an equal probability of landing heads up or tails up each time it is flipped , what is the probability that the coin will land heads up exectly twice in 3 consecutive flips ?

A. 0.125
B. 0.25
C. 0.375
D. 0.5
E. 0.666
[Reveal] Spoiler: OA
Expert Post
1 KUDOS received
CEO
CEO
User avatar
Joined: 17 Nov 2007
Posts: 3578
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 407

Kudos [?]: 2149 [1] , given: 359

GMAT ToolKit User Premium Member
 [#permalink] New post 27 Dec 2007, 03:12
1
This post received
KUDOS
Expert's post
C

P=nCm*p^m*q^(n-m)
n - the total number of trials.
m - the number of trials with heads.
n-m - the number of trials with tails.
p - probability of heads.
q - probability of tails.

P=3C2*(1/2)^2*(1/2)^1=3/8=0.375
3 KUDOS received
Manager
Manager
avatar
Joined: 26 Dec 2007
Posts: 70
Followers: 1

Kudos [?]: 15 [3] , given: 0

 [#permalink] New post 28 Dec 2007, 18:39
3
This post received
KUDOS
1
This post was
BOOKMARKED
this also works....

we know that we want 2 H and 1 T, so we have 3 possibilities

HHT
HTH
THH

find the probability of each and then add....
HHT= 1/2*1/2*1/2 = 1/8
HTH= 1/2*1/2*1/2 = 1/8
THH= 1/2*1/2*1/2 = 1/8

1/8+1/8+1/8= 3/8 or 0.375
Manager
Manager
avatar
Joined: 26 Feb 2007
Posts: 93
Followers: 1

Kudos [?]: 7 [0], given: 0

 [#permalink] New post 29 Dec 2007, 06:40
probability of 2 heads =3C2 *1/2^3 =3/8 =0.375
1 KUDOS received
Manager
Manager
avatar
Joined: 27 Oct 2008
Posts: 185
Followers: 1

Kudos [?]: 102 [1] , given: 3

Re: coin probability [#permalink] New post 27 Sep 2009, 10:34
1
This post received
KUDOS
If a coin has an equal probability of landing heads up or tails up each time it is flipped , what is the probability that the coin will land heads up exectly twice in 3 consecutive flips ?

A 0.125
B 0.25
C 0.375
D 0.5
E 0.666

Soln:
Total number of ways in which H or T can appear in 3 tosses of coin is
= 2 * 2 * 2 = 8 ways

For 2 H and 1 T
HHT, HTH, THH

Thus probability is
= P(HHT) + P(HTH) + P(THH)
= 1/8 + 1/8 + 1/8
= 3/8
= .375

Ans is C
Senior Manager
Senior Manager
User avatar
Status: Happy to join ROSS!
Joined: 29 Sep 2010
Posts: 279
Concentration: General Management, Strategy
Schools: Ross '14 (M)
Followers: 18

Kudos [?]: 106 [0], given: 48

Re: coin probability [#permalink] New post 29 Mar 2011, 07:56
It actually helps reading and understanding the problem correctly (:
I understood the question as 'what is the probability that the coin will land heads up consequently twice in 3 consecutive flips'?

In that case:
HHT = 1/8
THH = 1/8
Total outcomes: 8
Probability: 1/4
SVP
SVP
avatar
Joined: 16 Nov 2010
Posts: 1684
Location: United States (IN)
Concentration: Strategy, Technology
Followers: 31

Kudos [?]: 342 [0], given: 36

Premium Member Reviews Badge
Re: coin probability [#permalink] New post 29 Mar 2011, 18:23
3C2 * (1/2)^2(1/2)

= 3 * 1/8

= 0.375
_________________

Formula of Life -> Achievement/Potential = k * Happiness (where k is a constant)

GMAT Club Premium Membership - big benefits and savings

Intern
Intern
avatar
Joined: 07 Aug 2013
Posts: 30
Followers: 0

Kudos [?]: 4 [0], given: 1

Re: If a coin has an equal probability of landing heads up or [#permalink] New post 20 Sep 2013, 02:28
You can either determine that there are three outcomes (HTT, THT, TTH) that fit the criteria of use the formula 3C2 (3!/2!(3!-2!)

each outcome has a probality of 1/2*1/2*1/2 = 1/8

3 outocomes with P=1/8 = 3/8

1/8=0.125 or 3/8 is 0.375
GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 09 Sep 2013
Posts: 4792
Followers: 296

Kudos [?]: 53 [0], given: 0

Premium Member
Re: If a coin has an equal probability of landing heads up or [#permalink] New post 07 Dec 2014, 23:32
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

GMAT Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

Re: If a coin has an equal probability of landing heads up or   [#permalink] 07 Dec 2014, 23:32
    Similar topics Author Replies Last post
Similar
Topics:
When tossed, a certain coin has equal probability of landing on either young_gun 0 27 Apr 2015, 21:49
2 Experts publish their posts in the topic When tossed, a certain coin has equal probability of landing jet1445 8 28 Jul 2007, 08:53
When tossed, a cetain coin has equal probability of landing foolbox 5 09 Jun 2006, 18:25
When tossed, a certain coin has equal probability of landing joemama142000 2 13 Feb 2006, 20:41
If a coin has a probability of landing heads up or tails TeHCM 2 26 Dec 2005, 18:06
Display posts from previous: Sort by

If a coin has an equal probability of landing heads up or

  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®.