Question 142044: A fair coins is tossed 5 times.
What is the probability of obtaining exactly 3 heads?
I found a formula that looks like C(5,3)=5!/[3!(5-3)!]
My problem is, I don't know if this formula is right, or how to solve it. I believe this is supposed to tell you the number of possible outcomes???
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! A fair coins is tossed 5 times.
What is the probability of obtaining exactly 3 heads?
I found a formula that looks like C(5,3)=5!/[3!(5-3)!]
My problem is, I don't know if this formula is right, or how to solve it. I believe this is supposed to tell you the number of possible outcomes???
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You are correct; there are C(5,3) = 10 ways the 3 heads
can show up in the five tosses.
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Each of those patterns has probability (1/2)^3(1/2)^2 = (1/2)^5 = 1/32
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since the patterns are mutually exclusive you have to add up all those
probabilities to get:
10*1/32 = 5/16 as the probability of getting 3 heads when you throw
a coin 5 times.
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Cheers,
Stan H.
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