It is currently 25 Sep 2017, 01:13

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# PS: m 15 #31

Author Message
Manager
Joined: 05 Jan 2009
Posts: 81

Kudos [?]: 154 [0], given: 2

### Show Tags

20 Jun 2009, 12:05
If John throws a coin until a series of three consecutive heads or three consecutive tails appears, what is the probability that the game will end after the fourth throw?

(C) 2008 GMAT Club - m15#31

1/16
1/8
3/16
1/4
3/8

Kudos [?]: 154 [0], given: 2

Manager
Joined: 30 May 2009
Posts: 216

Kudos [?]: 129 [0], given: 0

Re: PS: m 15 #31 [#permalink]

### Show Tags

23 Jun 2009, 20:09

Probability of getting 3 consecutive heads and game ending in 4th turn is THHH = 1/16
Probability of getting 3 consecutive tails and game ending in 4th turn is HTTT = 1/16

1/16 + 1/16 = 1/8

What am I doing wrong???? This probability is a torture

Kudos [?]: 129 [0], given: 0

CIO
Joined: 02 Oct 2007
Posts: 1218

Kudos [?]: 970 [0], given: 334

Re: PS: m 15 #31 [#permalink]

### Show Tags

23 Jun 2009, 22:48
Hi,
Your solution is absolutely right! I guess you were confused by the copyright symbol (C) in the post above. It is not an OE.

sdrandom1 wrote:

Probability of getting 3 consecutive heads and game ending in 4th turn is THHH = 1/16
Probability of getting 3 consecutive tails and game ending in 4th turn is HTTT = 1/16

1/16 + 1/16 = 1/8

What am I doing wrong???? This probability is a torture

_________________

Welcome to GMAT Club!

Want to solve GMAT questions on the go? GMAT Club iPhone app will help.
Result correlation between real GMAT and GMAT Club Tests
Are GMAT Club Test sets ordered in any way?

Take 15 free tests with questions from GMAT Club, Knewton, Manhattan GMAT, and Veritas.

GMAT Club Premium Membership - big benefits and savings

Kudos [?]: 970 [0], given: 334

CIO
Joined: 02 Oct 2007
Posts: 1218

Kudos [?]: 970 [0], given: 334

Re: PS: m 15 #31 [#permalink]

### Show Tags

23 Jun 2009, 22:59
Hi pmal04,

Make sure you read the post in the last link carefully before posting another question in this forum.

Thank you for cooperation
pmal04 wrote:
If John throws a coin until a series of three consecutive heads or three consecutive tails appears, what is the probability that the game will end after the fourth throw?

(C) 2008 GMAT Club - m15#31

1/16
1/8
3/16
1/4
3/8

_________________

Welcome to GMAT Club!

Want to solve GMAT questions on the go? GMAT Club iPhone app will help.
Result correlation between real GMAT and GMAT Club Tests
Are GMAT Club Test sets ordered in any way?

Take 15 free tests with questions from GMAT Club, Knewton, Manhattan GMAT, and Veritas.

GMAT Club Premium Membership - big benefits and savings

Kudos [?]: 970 [0], given: 334

Re: PS: m 15 #31   [#permalink] 23 Jun 2009, 22:59
Display posts from previous: Sort by

# PS: m 15 #31

Moderator: Bunuel

 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®.