Logic / Unit 7 Logic 348 short lesson, about 20 seconds
The Negation Rule
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The idea
P(not-A) = 1 − P(A). For "at least one," compute the complement: 1 − P(none).
In practice
At least one six in four rolls: 1 − (5/6)⁴ ≈ 0.52.
Where people slip
"At least one" computed directly is a combinatorial swamp. The complement trick is the single most useful move in applied probability.
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