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A fair coin is flipped three times. What is the probability that the

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A fair coin is flipped three times. What is the probability that the  [#permalink]

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New post 21 Jan 2017, 18:57
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A fair coin is flipped three times. What is the probability that the coin lands on heads exactly twice?


A. \(\frac{1}{8}\)

B. \(\frac{3}{8}\)

C. \(\frac{1}{2}\)

D. \(\frac{5}{8}\)

E. \(\frac{7}{8}\)

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Re: A fair coin is flipped three times. What is the probability that the  [#permalink]

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New post 21 Jan 2017, 20:38
ziyuenlau wrote:
A fair coin is flipped three times. What is the probability that the coin lands on heads exactly twice?


A. \(\frac{1}{8}\)

B. \(\frac{3}{8}\)

C. \(\frac{1}{2}\)

D. \(\frac{5}{8}\)

E. \(\frac{7}{8}\)



Hi,

Ways of getting TWO heads in three flips..
3C2=3!/2!=3..

Total possible outcomes..
2*2*2=8..

Probability=3/8
B
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Re: A fair coin is flipped three times. What is the probability that the  [#permalink]

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New post 13 Aug 2017, 13:29
HHH
HHT
HTH
THH
TTT
TTH
THT
HTT

so there are 8 possible outcomes. 3 outcomes have only 2 heads. hence 3/8
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Re: A fair coin is flipped three times. What is the probability that the  [#permalink]

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New post 13 Aug 2017, 13:42
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hazelnut wrote:
A fair coin is flipped three times. What is the probability that the coin lands on heads exactly twice?


A. \(\frac{1}{8}\)

B. \(\frac{3}{8}\)

C. \(\frac{1}{2}\)

D. \(\frac{5}{8}\)

E. \(\frac{7}{8}\)


Probability of getting a head when a coin is flipped = 1/2
Probability of getting a tail when a coin is flipped = 1/2

Now coin is flipped thrice. The events in which coin lands in exactly 2 heads are THH, HTH, HHT

So required probability = 1/2*1/2*1/2 + 1/2*1/2*1/2 + 1/2*1/2*1/2 = 3/8

Answer B
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Re: A fair coin is flipped three times. What is the probability that the &nbs [#permalink] 13 Aug 2017, 13:42
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