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PS: m 15 #31

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pmal04
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PS: m 15 #31 [#permalink] New post   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

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sdrandom1
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Re: PS: m 15 #31 [#permalink] New post   23 Jun 2009, 20:09
How much ever I think about this problem, I am not getting (C). I am getting the answer as 2/16=1/8.

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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dzyubam
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Re: PS: m 15 #31 [#permalink] New post   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:
How much ever I think about this problem, I am not getting (C). I am getting the answer as 2/16=1/8.

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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dzyubam
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Re: PS: m 15 #31 [#permalink] New post   23 Jun 2009, 22:59
Hi pmal04,
Please do post your questions in the corresponding thread that is already discussing the question you're interested in. You can find this link m15-71875.html in here: gmat-club-tests-master-threads-all-tests-78599.html

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


Archived Topic
Hi there,
Archived GMAT Club Tests question - no more replies possible.
Where to now? Try our up-to-date Free Adaptive GMAT Club Tests for the latest questions.
Still interested? Check out the "Best Topics" block above for better discussion and related questions.
Thank you for understanding, and happy exploring!
GMAT Club Bot
gmatclubot
Re: PS: m 15 #31 [#permalink]
23 Jun 2009, 22:59
Moderator:
Bunuel
Math Expert
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