Probability Formula
Probability formulas and a topic-wise mock test for quantitative aptitude placement exams like TCS NQT, Infosys, and Wipro. Revise, then practice.
Key Probability Formulas
Probability Fundamentals - Chance and Likelihood
Probability measures the likelihood an event will occur, ranging from 0 (impossible) to 1 (certain).
- Probability = Favorable outcomes / Total outcomes
- Complement Rule: P(A) + P(A') = 1
- Union Rule: P(A∪B) = P(A) + P(B) - P(A∩B)
- Independent Events: P(A∩B) = P(A) × P(B)
- Conditional: P(A/B) = P(A∩B) / P(B)
- Example: Coin toss → P(Head) = 1/2; Dice → P(6) = 1/6
Special Probability Scenarios
Different experiments have different sample spaces and probability rules.
- Dice: Total outcomes = 6^n for n dice
- Coins: Total outcomes = 2^n for n coins
- Cards: Total outcomes = 52 for standard deck
- Geometric Probability = Area of favorable region / Total area
- Example: P(sum=7 with 2 dice) = 6/36 = 1/6
Advanced Probability Applications
Practical applications of probability concepts.
- Example 1: P(Head) = 1/2 = 50%
- Example 2: P(sum=7 with 2 dice) = 6/36 = 1/6
- Example 3: P(Ace from deck) = 4/52 = 1/13
- Example 4: Birthday problem (23 people) → P(at least 2 share) ≈ 50.7%
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