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probability question

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Junior | Next Rank: 30 Posts
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probability question

by levocap » Thu Aug 27, 2009 1:03 pm
If a fair coin is tossed three times, what is the probability that it will turn up heads exactly twice? The answer is 3/8. Is there a formulaic way to get this answer besides doing a counting tree?
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Master | Next Rank: 500 Posts
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by bharathh » Thu Aug 27, 2009 1:28 pm
A non-formulaic approach:

H = heads, T = tails

all possible outcomes for 3 tosses (should be 8)

HHH
TTT
THT
TTH
HTT

HHT
HTH
THH

There are 3 ways out of 8 to get the answer.... so 3/8
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by tohellandback » Thu Aug 27, 2009 9:04 pm
here:

https://www.beatthegmat.com/coin-flip-qu ... 17911.html
The powers of two are bloody impolite!!
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Junior | Next Rank: 30 Posts
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by nano124 » Sat Sep 05, 2009 7:06 am
It becomes very easy to solve when you use a decision tree diagram.
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