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

It is currently 25 Oct 2014, 14:12

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

When a certain coin is flipped, the probability of heads is

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Intern
Intern
avatar
Joined: 08 Oct 2012
Posts: 32
Followers: 1

Kudos [?]: 5 [0], given: 24

When a certain coin is flipped, the probability of heads is [#permalink] New post 28 Oct 2012, 17:47
2
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

70% (02:01) correct 30% (01:18) wrong based on 50 sessions
When a certain coin is flipped, the probability of heads is 0.5. If the coin is flipped 6 times, what is the probability that there are exactly 3 heads?

A. 1/4
B. 1/3
C. 5/16
D. 31/64
E. 1/2
[Reveal] Spoiler: OA

Last edited by Bunuel on 29 Oct 2012, 00:17, edited 2 times in total.
Renamed the topic.
Moderator
Moderator
User avatar
Joined: 02 Jul 2012
Posts: 1227
Location: India
Concentration: Strategy
GMAT 1: 740 Q49 V42
GPA: 3.8
WE: Engineering (Energy and Utilities)
Followers: 67

Kudos [?]: 719 [0], given: 116

Premium Member
Re: When a certain coin is flipped [#permalink] New post 28 Oct 2012, 21:27
kapsycumm wrote:
When a certain coin is flipped, the probability of heads is 0.5. If the coin is flipped 6 times, what is the probability that there are exactly 3 heads?

A. 1/4
B. 1/3
C. 5/16
D. 31/64
E. 1/2


Required series is HHHTTT = (\frac{1}{2})^6 = 1/64

This combination can occur in \frac{6!}{3!*3!} ways. ie 20 ways

So answer = \frac{1}{64}*20 = \frac{5}{16}

Kudos Please... If my post helped.
_________________

Did you find this post helpful?... Please let me know through the Kudos button.

Thanks To The Almighty - My GMAT Debrief

GMAT Reading Comprehension: 7 Most Common Passage Types

Expert Post
Veritas Prep GMAT Instructor
User avatar
Joined: 16 Oct 2010
Posts: 4877
Location: Pune, India
Followers: 1157

Kudos [?]: 5382 [0], given: 165

Re: When a certain coin is flipped [#permalink] New post 28 Oct 2012, 22:36
Expert's post
kapsycumm wrote:
When a certain coin is flipped, the probability of heads is 0.5. If the coin is flipped 6 times, what is the probability that there are exactly 3 heads?

A. 1/4
B. 1/3
C. 5/16
D. 31/64
E. 1/2


Out of 6 tosses, exactly 3 heads implies exactly 3 tails.
You can get 3 heads and 3 tails in various ways: HHHTTT, HHTHTT, TTTHHH etc
How many such ways are there? We just need to find the number of ways of arranging 3 Hs and 3 Ts in a row. This can be done in 6!/3!*3! = 20 ways (the 3 Hs are identical and the 3 Ts are identical)

Probability of obtaining HHHTTT = (0.5)*(0.5)*(0.5)*(0.5)*(0.5)*(0.5)

Probability of obtaining 3Hs and 3 Ts in any order = (0.5)^6 * 20 = 5/16

Check out this post for a discussion on binomial probability concept:
http://www.veritasprep.com/blog/2012/02 ... obability/
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Save $100 on Veritas Prep GMAT Courses And Admissions Consulting
Enroll now. Pay later. Take advantage of Veritas Prep's flexible payment plan options.

Veritas Prep Reviews

Expert Post
1 KUDOS received
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 23422
Followers: 3617

Kudos [?]: 28972 [1] , given: 2874

Re: When a certain coin is flipped, the probability of heads is [#permalink] New post 29 Oct 2012, 00:17
1
This post received
KUDOS
Expert's post
When a certain coin is flipped, the probability of heads is 0.5. If the coin is flipped 6 times, what is the probability that there are exactly 3 heads?

A. 1/4
B. 1/3
C. 5/16
D. 31/64
E. 1/2

We need the proability of HHHTTT (any combination of this): P=\frac{6!}{3!3!}*(\frac{1}{2})^6=\frac{20}{64}=\frac{5}{16}. We are multiplying by \frac{6!}{3!3!} since HHHTTT scenario can occur in several ways: HHHTT, THHHTT, TTHHHT, ... basically the number of permutations of 6 letters HHHTTT, out of which 3 H's and T's are identical (\frac{6!}{3!3!});

Answer: C.

Check similar questions to practice:
what-is-the-probability-that-a-field-gun-will-hit-thrice-on-127334.html
there-is-a-90-chance-that-a-registered-voter-in-burghtown-56812.html
combination-ps-55071.html
the-probability-that-a-family-with-6-children-has-exactly-88945.html
if-a-certain-coin-is-flipped-the-probability-that-the-coin-58357.html
what-is-the-probability-that-a-field-gun-will-hit-thrice-on-127334.html
a-store-buys-10-bottles-of-alcohol-including-7-bottles-of-55071.html
the-probability-that-a-family-with-6-children-has-exactly-88945.html
a-gumball-machine-contains-7-blue-5-green-and-4-red-141079.html
a-basket-contains-3-blue-3-red-and-3-yellow-marbles-if-55673.html
there-are-10-solid-colored-balls-in-a-box-including-1-green-135103.html
when-a-random-experiment-is-conducted-the-probability-that-89835.html
if-the-probability-of-sita-getting-selected-to-a-school-is-130643.html
in-a-multiple-choice-test-comprising-5-questions-each-with-136936.html
if-a-certain-coin-is-flipped-the-probability-that-the-coin-58357.html


Probability chapter of out Math Book:
math-probability-87244.html

Hope it helps.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

COLLECTION OF QUESTIONS:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS ; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
25 extra-hard Quant Tests

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Re: When a certain coin is flipped, the probability of heads is   [#permalink] 29 Oct 2012, 00:17
    Similar topics Author Replies Last post
Similar
Topics:
If a certain coin is flipped, the probability that the coin seofah 1 15 Nov 2008, 10:15
If a certain coin is flipped, the probability that the coin haichao 1 09 Nov 2008, 18:19
4 Experts publish their posts in the topic If a certain coin is flipped, the probability that the coin marcodonzelli 21 12 Jan 2008, 02:44
If a certain coin is flipped, the probability that the coin WinIT 1 12 Nov 2006, 08:49
If a certain coin is flipped, the probability that the coin getzgetzu 7 05 May 2006, 22:04
Display posts from previous: Sort by

When a certain coin is flipped, the probability of heads is

  Question banks Downloads My Bookmarks Reviews Important topics  


cron

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®.