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# PS: m 15 #31

Author Message
Manager
Joined: 05 Jan 2009
Posts: 82
Followers: 1

Kudos [?]: 94 [0], given: 2

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20 Jun 2009, 11:05
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
Manager
Joined: 30 May 2009
Posts: 218
Followers: 5

Kudos [?]: 120 [0], given: 0

Re: PS: m 15 #31 [#permalink]

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23 Jun 2009, 19:09

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
CIO
Joined: 02 Oct 2007
Posts: 1218
Followers: 94

Kudos [?]: 911 [0], given: 334

Re: PS: m 15 #31 [#permalink]

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23 Jun 2009, 21:48
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

_________________

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CIO
Joined: 02 Oct 2007
Posts: 1218
Followers: 94

Kudos [?]: 911 [0], given: 334

Re: PS: m 15 #31 [#permalink]

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23 Jun 2009, 21:59
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

Re: PS: m 15 #31   [#permalink] 23 Jun 2009, 21:59
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# PS: m 15 #31

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