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A fair coin is tossed 5 times. What is the probability of [#permalink]
 20 Aug 2010, 05:39
Question Stats:
15% (01:53) correct
84% (01:03) wrong based on 0 sessions
A fair coin is tossed 5 times. What is the probability of getting at least three heads on consecutive tosses? A. 2/16 B. 1/4 C. 7/24 D. 5/16 E. 15/32
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Re: Hard probability ! [#permalink]
20 Aug 2010, 05:59
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Director
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Re: Hard probability ! [#permalink]
21 Aug 2010, 00:04
Awesome explanation Bunuel ! 
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Re: Hard probability ! [#permalink]
21 Aug 2010, 00:50
Brunnel explained it in detail. I would just count the number of possibilities and divide it by 2^n
HHHHH
HHHTT
HHHHT
THHHT
TTHHH
HHHTH
THHHH
HTHHH
8/(2)^5 ==> 8/32 ==> 1/4
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Re: Hard probability ! [#permalink]
21 Aug 2010, 13:54
All possible events = (1/2)^5= 1/32 all the favorable events HHHHH HHHTT THHHT TTHHH HHHHT THHHH that makes 6 favourable events Hence answer will 6/32 = 1/4 therefore B
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Re: Hard probability ! [#permalink]
23 Aug 2011, 17:11
my question is how do you determine from this problem, that immediately, you are going to have to map out the possibilities?
there seems to be no nifty way to do it other than really just exhausting the possibilities?
thanks
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Re: Hard probability ! [#permalink]
23 Aug 2011, 17:51
Bunuel - U rock. +1 for you. Cheers.!
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Re: Hard probability ! [#permalink]
27 Dec 2011, 05:23
This is like another probability question asked in the forum, bunnel explained that very well.
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Re: Hard probability ! [#permalink]
31 Dec 2011, 06:14
how common is "coin" probability question in real GMAT?
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A fair coin is tossed 5 times. What is the probability of getting at least three heads on consecutive tosses? A. 3/16 B. 1/4 C. 7/24 D. 5/16 E. 15/32 Kaplan says the answer is 1/4. I think the answer is 3/16 because I have interpreted the qn as: What is the probability of getting atleast 3 consecutive heads -> 3 consecutive heads or 4 consecutive heads or 5 consecutive heads ?
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Re: PS: Probability [#permalink]
24 Mar 2012, 13:02
shahlanuk wrote: A fair coin is tossed 5 times. What is the probability of getting at least three heads on consecutive tosses? A. 3/16 B. 1/4 C. 7/24 D. 5/16 E. 15/32 Kaplan says the answer is 1/4. I think the answer is 3/16 because I have interpreted the qn as: What is the probability of getting atleast 3 consecutive heads -> 3 consecutive heads or 4 consecutive heads or 5 consecutive heads ? I agree with you I too got A, Experts please help!
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Re: PS: Probability [#permalink]
24 Mar 2012, 14:29
shahlanuk wrote: A fair coin is tossed 5 times. What is the probability of getting at least three heads on consecutive tosses? A. 3/16 B. 1/4 C. 7/24 D. 5/16 E. 15/32 Kaplan says the answer is 1/4. I think the answer is 3/16 because I have interpreted the qn as: What is the probability of getting atleast 3 consecutive heads -> 3 consecutive heads or 4 consecutive heads or 5 consecutive heads ? Merging similar topics. Your interpretation is correct: at least 3 consecutive heads means 3, 4, or 5 consecutive heads, but the answer is still 1/4. Please check the solution provided above and ask if anything remains unclear.
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A fair coin is tossed 5 times. [#permalink]
13 Nov 2012, 21:24
A fair coin is tossed 5 times, what is the probability of getting at least 3 heads on consecutive tosses?
-- Ans will be provided later.
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Re: A fair coin is tossed 5 times. [#permalink]
13 Nov 2012, 21:31
bellcurve wrote: A fair coin is tossed 5 times, what is the probability of getting at least 3 heads on consecutive tosses?
-- Ans will be provided later. Favorable outcomes: HHHHH -- All heads HHHHT -- 4 heads THHHH HHHTT -- 3 heads THHHT TTHHH HTHHH HHHTH Total possiblities = 2^5 = 32 Favorable = 8 Probability = 8/32 = 1/4 Hope it helps! PS: Please provide atleast options if not OA.
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Re: A fair coin is tossed 5 times. [#permalink]
13 Nov 2012, 23:02
at least consecutive 3 heads
max consecutive 5 heads
5 heads - HHHHH (1 way)
4 heads - THHHH, HHHHT (2 ways)
3 heads - HHHTH, HHHTT, THHHT, HTHHH, TTHHH (5 ways)
Total 8 ways
Total no ways irrespective of outcome= 2x2x2x2x2 = 32
probability of atleast 3 consecutive heads = 8/32 or .25
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Re: A fair coin is tossed 5 times. [#permalink]
14 Nov 2012, 03:15
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Re: A fair coin is tossed 5 times.
[#permalink]
14 Nov 2012, 03:15
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