Probability Practice
Apply the addition and multiplication rules, tell independent from dependent events, and count with permutations and combinations.
1 Practice
Type your answer and press Check answer (or Enter). A wrong answer earns a hint; a second miss earns a stronger hint; a third miss walks you through the full solution. Scores and streaks are session-only.
2 What you’ll practice
Every problem is generated fresh from templates across several question types — a problem never repeats until its whole pool is used up.
Basic probability
Favorable over total.
Addition rule
Add, then subtract the overlap.
Independent events
Multiply when independent.
Without replacement
Recompute after each draw.
Permutations
Order matters: P(n,k).
Combinations
Order free: C(n,k).
Complement
One minus the opposite.
3 Watch out for these
The mistakes students make most often on these problems.
P(A or B) = P(A) + P(B) − P(A and B). The Venn overlap is counted twice if you just add.
Choosing people is a combination — order does not matter. P(n,k) overcounts by k!.
Without replacement, the second probability changes: P(B|A) uses the new totals.