Probability questions on the SAT require a solid understanding of basic probability concepts and how to apply them to real-world scenarios.
On the Digital SAT exam, probability questions ask you to determine how likely a particular event is to occur. With 2 math modules and 44 questions total, there is a very good chance at least one probability question will show up (usually one or two per exam).
Probability is the measure of how likely an event is to occur. It is expressed as a fraction: number of desired outcomes divided by total possible outcomes. For example, the probability of tails on a coin flip is 1/2.
Finding the probability of a single event. Example: 5 red and 5 blue marbles. P(red) = 5/10 = 1/2.
Two or more events together. Example: Two red marbles in a row without replacement: (5/10) x (4/9) = 2/9.
One event or another. Example: P(ace or queen) = 4/52 + 4/52 = 8/52 = 2/13.
Probability given a condition. Example: 52 dancers, 14 are ballet. P(ballet | dancer) = 14/52 = 7/26.
Simple: Look for questions about a single event. Compound: Multiple events together. Either/Or: One event or another. Conditional: Look for "given" or "assuming."
P(E) = Number of favorable outcomes / Total possible outcomes
Independent events: P(A and B) = P(A) x P(B). Dependent events: P(A and B) = P(A) x P(B|A).
Mutually exclusive: P(A or B) = P(A) + P(B). Non-mutually exclusive: P(A or B) = P(A) + P(B) - P(A and B).
P(B|A) = P(A and B) / P(A). Focus on the subset meeting the condition.
Check your work to ensure your answer makes sense. Re-read the question and confirm the correct type and formula were used.