Probability Basics
Calculate probabilities and understand basic probability concepts.
Practice Problems
3 red, 4 blue, 5 green
Flip coin twice, P(HH)?
Pro Tips & Shortcuts
SAT Tip: Probability can be expressed as fraction, decimal, or percent.
SAT Tip: For "at least one" problems, use complement: P(at least 1) = 1 - P(none).
SAT Tip: Coin flips, dice rolls, and draws with replacement are typically independent.
SAT Tip: Always simplify fractions in probability.
SAT Tip: Each flip is independent - the first result doesn't affect the second.
Count favorable outcomes and total outcomes carefully.
Complement is useful when it's easier to calculate what doesn't happen.
AND means multiply, OR means add (for mutually exclusive events).
Total marbles = 12, blue = 4, so P = 4/12 = 1/3.
For multiple independent events, multiply their probabilities.