Cue Column:

• What is the sample space?
• When are outcomes equally likely?
• What is the complement rule?

Note Column: The sample space S is the set of all possible outcomes. When all outcomes are equally likely, P(A) = n$\frac{A}{n}$(S). The complement rule P(A') = 1 - P(A) is the fastest route for "at least one" problems. For two events: P(A union B) = P(A) + P(B) - P(A intersect B). Mutually exclusive events have P(A intersect B) = 0, so P(A union B) = P(A) + P(B).

Summary: Classical probability relies on counting favorable outcomes over total outcomes. The complement rule and addition rule are the two most frequently used tools in JEE.