Discussion
A coin is tossed five times. What is the probability that there is at least one tail?
Answer: A
Five tosses give \( 2^{5} = 32 \) outcomes. Only one of them - all heads - has no tail, so use the complement.
\[ P(\text{no tail}) = \frac{1}{32} \]
\[ P(\text{at least one tail}) = 1 - \frac{1}{32} = \frac{31}{32} \]
"At least one" is almost always easier through the complement than by counting one, two, three, four and five tails separately.
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