It is currently 23 Oct 2017, 14:08

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.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

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

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Intern
Intern
avatar
Joined: 21 Nov 2007
Posts: 11

Kudos [?]: 10 [0], given: 0

If a coin has an equal probability of landing heads up or [#permalink]

Show Tags

New post 27 Dec 2007, 02:43
11
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

63% (00:46) correct 37% (00:42) wrong based on 625 sessions

HideShow timer Statistics

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

Kudos [?]: 10 [0], given: 0

Expert Post
2 KUDOS received
CEO
CEO
User avatar
Joined: 17 Nov 2007
Posts: 3584

Kudos [?]: 4596 [2], given: 360

Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
GMAT ToolKit User Premium Member
 [#permalink]

Show Tags

New post 27 Dec 2007, 04:12
2
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

Kudos [?]: 4596 [2], given: 360

3 KUDOS received
Manager
Manager
avatar
Joined: 26 Dec 2007
Posts: 70

Kudos [?]: 25 [3], given: 0

 [#permalink]

Show Tags

New post 28 Dec 2007, 19:39
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

Kudos [?]: 25 [3], given: 0

Manager
Manager
avatar
Joined: 26 Feb 2007
Posts: 92

Kudos [?]: 8 [0], given: 0

 [#permalink]

Show Tags

New post 29 Dec 2007, 07:40
probability of 2 heads =3C2 *1/2^3 =3/8 =0.375

Kudos [?]: 8 [0], given: 0

1 KUDOS received
Manager
Manager
avatar
Joined: 27 Oct 2008
Posts: 185

Kudos [?]: 164 [1], given: 3

Re: coin probability [#permalink]

Show Tags

New post 27 Sep 2009, 11:34
1
This post received
KUDOS
1
This post was
BOOKMARKED
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

Kudos [?]: 164 [1], given: 3

Senior Manager
Senior Manager
User avatar
Status: Happy to join ROSS!
Joined: 29 Sep 2010
Posts: 273

Kudos [?]: 132 [0], given: 48

Concentration: General Management, Strategy
Schools: Ross '14 (M)
Reviews Badge
Re: coin probability [#permalink]

Show Tags

New post 29 Mar 2011, 08:56
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

Kudos [?]: 132 [0], given: 48

SVP
SVP
avatar
Joined: 16 Nov 2010
Posts: 1594

Kudos [?]: 592 [0], given: 36

Location: United States (IN)
Concentration: Strategy, Technology
Premium Member Reviews Badge
Re: coin probability [#permalink]

Show Tags

New post 29 Mar 2011, 19:23
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

Kudos [?]: 592 [0], given: 36

Intern
Intern
avatar
Joined: 07 Aug 2013
Posts: 29

Kudos [?]: 6 [0], given: 1

Re: If a coin has an equal probability of landing heads up or [#permalink]

Show Tags

New post 20 Sep 2013, 03:28
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

Kudos [?]: 6 [0], given: 1

GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 09 Sep 2013
Posts: 16535

Kudos [?]: 274 [0], given: 0

Premium Member
Re: If a coin has an equal probability of landing heads up or [#permalink]

Show Tags

New post 08 Dec 2014, 00:32
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

Kudos [?]: 274 [0], given: 0

Director
Director
User avatar
Joined: 10 Mar 2013
Posts: 592

Kudos [?]: 463 [0], given: 200

Location: Germany
Concentration: Finance, Entrepreneurship
GMAT 1: 580 Q46 V24
GPA: 3.88
WE: Information Technology (Consulting)
GMAT ToolKit User
If a coin has an equal probability of landing heads up or [#permalink]

Show Tags

New post 19 Jan 2016, 13:42
Richard Lee wrote:
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


Probability * # of arrangements --> \(1/2^3*3=0,375\)
_________________

When you’re up, your friends know who you are. When you’re down, you know who your friends are.

Share some Kudos, if my posts help you. Thank you !

800Score ONLY QUANT CAT1 51, CAT2 50, CAT3 50
GMAT PREP 670
MGMAT CAT 630
KAPLAN CAT 660

Kudos [?]: 463 [0], given: 200

GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 09 Sep 2013
Posts: 16535

Kudos [?]: 274 [0], given: 0

Premium Member
Re: If a coin has an equal probability of landing heads up or [#permalink]

Show Tags

New post 21 Jul 2017, 08:18
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

Kudos [?]: 274 [0], given: 0

Re: If a coin has an equal probability of landing heads up or   [#permalink] 21 Jul 2017, 08:18
Display posts from previous: Sort by

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

  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 | Emoji artwork provided by EmojiOne

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®.