Five fair coins are tossed. What is the probability that exactly three of the coins land tails side up?
a) 5/32
b) 3/16
c) 5/16
d) 3/8
e) 5/8
The OA is c but i don't know how to solve it.
Probability
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For coin flips we know that the number of possible outcomes is always 2^n, where n is the number of flips.gmatguy16 wrote:since only heads or tails is possible we can use binomial distribution ..
answer is 5 c 3 (0.5) ^ 3 (0.5) ^ (5-3) = 10(0.5) ^ 3 (0.5 )^ 2 = 5/16
So, the generic formula is:
nCk/2^n
where n is the number of flips and k is the number of results you want to get.
In this question, we have n=5 and k=3, so we'd have:
5C3/2^5
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