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Suppose you flip a fair coin six times. What is the probabi

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Magoosh GMAT Instructor
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Joined: 28 Dec 2011
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Kudos [?]: 3070 [0], given: 38

Suppose you flip a fair coin six times. What is the probabi [#permalink] New post 02 Jan 2013, 13:12
Expert's post
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

86% (01:36) correct 14% (01:38) wrong based on 44 sessions
Suppose you flip a fair coin six times. What is the probability that, in six flips, you get at least one head?

(A) 5/8
(B) 13/16
(C) 15/16
(D) 31/32
(E) 63/64


For a complete discussion of "at least" questions, as well as full explanation of this problem, see this post:
http://magoosh.com/gmat/2012/gmat-math- ... -question/

Mike :-)
[Reveal] Spoiler: OA

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Mike McGarry
Magoosh Test Prep

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Last edited by Bunuel on 03 Jan 2013, 01:55, edited 1 time in total.
Renamed the topic.
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Joined: 18 Oct 2011
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Location: United States
Concentration: Entrepreneurship, Marketing
GMAT Date: 01-30-2013
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Kudos [?]: 38 [0], given: 0

Re: Suppose you flip a fair coin six times. What is the probabi [#permalink] New post 03 Jan 2013, 12:44
Best way of solving an "at least 1" type of question is to compute "1 - probability of flipping 0 heads"

probability of flipping either a head or a tail = 1/2

probability of flipping 6 tails in a row (1/2)^6

probability of flipping at least 1 head = 1 - (1/2)^6 = 63/64 (answer E)
Re: Suppose you flip a fair coin six times. What is the probabi   [#permalink] 03 Jan 2013, 12:44
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Suppose you flip a fair coin six times. What is the probabi

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