Theoretical Probability
Theoretical probability is calculated using known facts about a situation, rather than by running trials. It uses the formula:
P(event) = Number of favourable outcomes ÷ Total number of possible outcomes
Worked Example
A bag contains 10 marbles: 4 are red. P(red) = 4/10 = 2/5.
Theoretical probability assumes every outcome is equally likely — it's calculated, not measured.
Practice: Theoretical Probability
Calculate a theoretical probability or count favourable outcomes.