How to use it
Type the problem as it is written, for example "two cards are drawn without replacement; find P(both aces)". Use ^ for powers and / for fractions.
Read the solution. It comes as numbered steps, each naming the rule it uses, and ends with the final answer.
If a step is unclear, ask about it in your own words, such as "explain step 2". Ask for a similar problem to try one yourself.
What the probability solver covers
- Basic probability and complements
- Counting: permutations and combinations
- Independent and dependent events
- Conditional probability and Bayes' theorem
- Expected value
- Binomial, geometric and normal distributions; for data sets and tests, use the statistics solver
Worked example: two aces
The first card is an ace with probability 4/52. One ace is gone, so the second is an ace with probability 3/51.
P(both aces) = 4/52 × 3/51 = 12/2652 = 1/221.
Common mistakes
- Adding the probabilities of events that can happen together. P(A or B) = P(A) + P(B) − P(A and B).
- Treating draws without replacement as independent.
- Using permutations when order doesn't matter.
- Swapping P(A | B) and P(B | A).
Questions students ask
Should I give the answer as a fraction or a decimal?
Ask for either. By default the solver keeps exact fractions and adds a decimal where it helps.
Can it explain why, not only how?
Yes. Ask why a step works, for example why the events are independent, and it explains the reasoning. For puzzles like the Monty Hall problem, see these hard math questions.
Do I need an account?
No. You can type or dictate problems without signing in. Signing in with Google or Discord is free; it keeps your chats beyond 3 days and lets you attach a photo, PDF or Word file.