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If a coin has an equal probability of landing heads up or [#permalink]

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27 Dec 2007, 02:43

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If a coin has an equal probability of landing heads up or tails up each time it is flipped , what is the probability that the coin will land heads up exectly twice in 3 consecutive flips ?

P=nCm*p^m*q^(n-m)
n - the total number of trials.
m - the number of trials with heads.
n-m - the number of trials with tails.
p - probability of heads.
q - probability of tails.

If a coin has an equal probability of landing heads up or tails up each time it is flipped , what is the probability that the coin will land heads up exectly twice in 3 consecutive flips ?

A 0.125 B 0.25 C 0.375 D 0.5 E 0.666

Soln: Total number of ways in which H or T can appear in 3 tosses of coin is = 2 * 2 * 2 = 8 ways

For 2 H and 1 T HHT, HTH, THH

Thus probability is = P(HHT) + P(HTH) + P(THH) = 1/8 + 1/8 + 1/8 = 3/8 = .375

It actually helps reading and understanding the problem correctly (: I understood the question as 'what is the probability that the coin will land heads up consequently twice in 3 consecutive flips'?

In that case: HHT = 1/8 THH = 1/8 Total outcomes: 8 Probability: 1/4

Re: If a coin has an equal probability of landing heads up or [#permalink]

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08 Dec 2014, 00:32

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If a coin has an equal probability of landing heads up or [#permalink]

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19 Jan 2016, 13:42

Richard Lee wrote:

If a coin has an equal probability of landing heads up or tails up each time it is flipped , what is the probability that the coin will land heads up exectly twice in 3 consecutive flips ?

A. 0.125 B. 0.25 C. 0.375 D. 0.5 E. 0.666

Probability * # of arrangements --> \(1/2^3*3=0,375\)
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