5.3.4—Elementary probability

For equally likely outcomes, P(A)=number favourable/number total. For unequal outcomes, use the given probabilities and ensure they sum to one.

Define the sample space, avoid counting outcomes with different probabilities as equal, and use complements when the direct event is cumbersome.

The probability of at least one six in two fair rolls is 1−(5/6)²=11/36.

“At least one” includes two occurrences; subtracting only the probability of exactly one misses cases.