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Joined: 21 Nov 2007
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If a coin has an equal probability of landing heads up or
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27 Dec 2007, 02:43
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67% (01:09) correct 33% (01:12) wrong based on 566 sessions
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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 ? A. 0.125 B. 0.25 C. 0.375 D. 0.5 E. 0.666
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Manager
Joined: 26 Dec 2007
Posts: 68

this also works....
we know that we want 2 H and 1 T, so we have 3 possibilities
HHT
HTH
THH
find the probability of each and then add....
HHT= 1/2*1/2*1/2 = 1/8
HTH= 1/2*1/2*1/2 = 1/8
THH= 1/2*1/2*1/2 = 1/8
1/8+1/8+1/8= 3/8 or 0.375




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C
P=nCm*p^m*q^(nm)
n  the total number of trials.
m  the number of trials with heads.
nm  the number of trials with tails.
p  probability of heads.
q  probability of tails.
P=3C2*(1/2)^2*(1/2)^1=3/8=0.375



Manager
Joined: 26 Feb 2007
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probability of 2 heads =3C2 *1/2^3 =3/8 =0.375



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Re: coin probability
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27 Sep 2009, 11:34
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
Ans is C



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Re: coin probability
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29 Mar 2011, 08:56
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



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Re: coin probability
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29 Mar 2011, 19:23
3C2 * (1/2)^2(1/2) = 3 * 1/8 = 0.375
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Re: If a coin has an equal probability of landing heads up or
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20 Sep 2013, 03:28
You can either determine that there are three outcomes (HTT, THT, TTH) that fit the criteria of use the formula 3C2 (3!/2!(3!2!)
each outcome has a probality of 1/2*1/2*1/2 = 1/8
3 outocomes with P=1/8 = 3/8
1/8=0.125 or 3/8 is 0.375



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If a coin has an equal probability of landing heads up or
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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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Re: If a coin has an equal probability of landing heads up or
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22 Feb 2019, 16:37
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 bWe need to determine the probability of HHT and its variations: P(HHT) = (1/2)^3 = 1/8 Since we can arrange HHT in 3!/2! = 3 ways, the overall probability is 3 x 1/8 = 3/8 = 0.375. Answer: C
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Re: If a coin has an equal probability of landing heads up or
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22 Feb 2019, 18:02
Another way to do this: if you flip a coin an odd number of times, half the time you get more heads than tails, and half the time you get more tails than heads. You get three heads (1/2)^3 = 1/8 of the time, and since the only other way to get more heads than tails is to get two heads, that must happen 3/8 of the time.
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Re: If a coin has an equal probability of landing heads up or
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22 Feb 2019, 18:02






