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

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Joined: 14 Nov 2016
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A fair coin is flipped three times. What is the probability that the  [#permalink]

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21 Jan 2017, 18:57
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74% (00:47) correct 26% (01:07) wrong based on 205 sessions

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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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Posts: 7609
Re: A fair coin is flipped three times. What is the probability that the  [#permalink]

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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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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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13 Aug 2017, 13:42
1
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

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