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Robert tossed a fair coin 3 times. What is the probability that the co

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Math Expert
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Joined: 02 Sep 2009
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Robert tossed a fair coin 3 times. What is the probability that the co  [#permalink]

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New post 27 Dec 2015, 09:04
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

75% (01:05) correct 25% (01:18) wrong based on 174 sessions

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Joined: 20 Feb 2015
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Re: Robert tossed a fair coin 3 times. What is the probability that the co  [#permalink]

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New post 30 Dec 2015, 04:51
Total outcomes = HHH HHT HTT HTH TTT TTH THT THH
required = HHT HTH THH
probability =3/8=0.375
Marshall & McDonough Moderator
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Re: Robert tossed a fair coin 3 times. What is the probability that the co  [#permalink]

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New post 30 Dec 2015, 04:57
Total number of outcomes = 2 * 2 * 2 = 8
Out of 3 times we need heads exactly 2 times = 3C2 = 3

Probability = 3/8 = 0.375
Math Revolution GMAT Instructor
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Re: Robert tossed a fair coin 3 times. What is the probability that the co  [#permalink]

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New post 30 Dec 2015, 05:49
Forget conventional ways of solving math questions. In PS, IVY approach is the easiest and quickest way to find the answer.

Robert tossed a fair coin 3 times. What is the probability that the coin landed heads up exactly twice?

A. 0.125
B. 0.250
C. 0.375
D. 0.750
E. 0.875



The probability is exactly same as the cion landed tail up once. That is 3*(1/2)^3 = 3/8 =0.375.


The answer is, therefore, (C).
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Re: Robert tossed a fair coin 3 times. What is the probability that the co  [#permalink]

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New post 02 Apr 2016, 05:49
possible outcomes after tossing a fair coin 3 times:
HHH
HHT
HTH
HTT
THH
THT
TTH
TTT

out of that only 3 favourable cases are required
probability = 3/8 = 0.375
Answer - C
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New post 24 Mar 2018, 10:54
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Re: Robert tossed a fair coin 3 times. What is the probability that the co   [#permalink] 24 Mar 2018, 10:54
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