Mathematics - Probability - Introduction - Basic probability concepts - Probability Formula

7 steps: (1) P(event) = favorable outcomes / total possible outcomes. (2) Example: fair die. P(rolling 3) = 1/6 (one favorable, six total). (3) P(rolling even) = 3/6 = 1/2 (three favorable: 2,4,6). (4) Example: bag with 4 red, 3 blue, 2 green marbles. P(red) = 4/9. (5) Complement: P(NOT red) = 1 - P