PS: m 15 #31

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Joined: 05 Jan 2009

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PS: m 15 #31 [#permalink]

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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Manager

Joined: 30 May 2009

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Re: PS: m 15 #31 [#permalink]

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

CIO

Joined: 02 Oct 2007

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Re: PS: m 15 #31 [#permalink]

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:

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CIO

Joined: 02 Oct 2007

Posts: 1261

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Re: PS: m 15 #31 [#permalink]

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:

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Re: PS: m 15 #31 [#permalink] 23 Jun 2009, 22:59

		Similar topics	Author	Replies	Last post
Similar Topics:		ps #15	bmwhype2	6	29 May 2007, 01:55
	3	PS - Factor (m04q31)	rao	16	17 Sep 2008, 14:34
		PS: m 15 #6	pmal04	1	20 Jun 2009, 12:21
		PS: m 15 #10	pmal04	2	20 Jun 2009, 12:34
		PS: m 15 #18	pmal04	1	20 Jun 2009, 13:01

PS: m 15 #31

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PS: m 15 #31

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