Probability notes
OpenThe 4 formulas you need for Probability, on one page.
For explanations and lectures, see the full topic page. Then test yourself with 9 JEE Main 2026 PYQs.
Maths · printable
Probability: One-Page Formula Sheet
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Last updated: 26 October 2026
Formula sheet
Probability formulas
Probability — formula sheet
Formulas
- P(A|B) = P(A ∩ B)/P(B)
- Bayes: P(Eᵢ|A) = P(Eᵢ)P(A|Eᵢ)/Σ P(Eⱼ)P(A|Eⱼ)
- Binomial: P(X = r) = ⁿCᵣ pʳ qⁿ⁻ʳ; mean np, variance npq
- P(at least one) = 1 − P(none)
Key ideas
- P(A ∪ B) = P(A) + P(B) − P(A ∩ B)
- Independent: P(A ∩ B) = P(A)P(B)
- Bayes' theorem reverses conditional probability
- Binomial: n independent trials, constant p
Traps to avoid
- Confusing independent and mutually exclusive events
- Wrong sample space size
- Forgetting order in sampling without replacement
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FAQs
Frequently asked questions
Where can I get a Probability formula sheet PDF for free?
On this page. Use the print button and choose 'Save as PDF'.
How should I use a formula sheet?
Read it once a day for a week, then cover it and write the formulas from memory. Revise only the ones you missed.