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What is the probability of getting $3$ heads in a row? Would it be $\frac 18$?

assuming the coin is a fair one.

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Why do you think it would be 1/8? – Joseph Weissman Dec 2 '10 at 20:16

If you are assuming 3 coin tosses of a fair coin, then there are $2\times 2\times 2=8$ outcomes. Three consective heads can occur only one way. So, yes, the probability is $\frac{1}{8}$

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What id you only have 1 coin? And then toss it three times? Wouldnt it just be 1/2 since its independent tosses? – Ross James Dec 2 '10 at 19:40
Tossing one coin three times is essentially the same as tossing 3 coins. By your way of thinking, you can think the probability at each stage is $\frac{1}{2}$ and probability of the compound event is the product of probability of independent events, so it's $\frac{1}{2} \cdot \frac{1}{2} \cdot \frac{1}{2} =\frac{1}{8}$ – Timothy Wagner Dec 2 '10 at 19:43
But if you didnt know if it was heads or tails and if someone else did....would the probabilities change? E.g. suppose you were blindfolded. – Ross James Dec 2 '10 at 19:49

Assuming a fair coin, how many sequences of three throws are there? Are they equally likely? How many of those are "3 heads in a row"?

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