Answer: A) 5.4%
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Explanation:
We use the binomial probability formula here
P(k) = (n C k)*(p)^k*(1-p)^(n-k)
In this case, there are n = 12 trials and p = 0.5 is the probability of getting heads. The value of k = 3 means we want 3 heads.
So,
P(k) = (n C k)*(p)^k*(1-p)^(n-k)
P(3) = (12 C 3)*(0.5)^3*(1-0.5)^(12-3)
P(3) = 220*(0.5)^3*(1-0.5)^(12-3)
P(3) = 0.0537109375
P(3) = 0.054
P(3) = 5.4%
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Side note: the n C k refers to the nCr combination formula
[tex]_n C _r = \frac{n!}{r!*(n-r)!}[/tex]
where the exclamation marks mean factorials. You could also use Pascal's Triangle as an alternative for this portion.
