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Probability — Revision Notes

Tamil Nadu Board · Class 9 · Mathematics

Probability revision notes for Tamil Nadu Board Class 9 Mathematics: 4 topics in quick points. Part of the Tamil Nadu Board Class 9 Mathematics syllabus.

44 questions28 flashcards5 formulas & key relations5 concepts

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A diagram illustrating a random experiment (e.g., rolling a fair six-sided die) showing all possible outcomes and how they form the sample space. Each outcome is distinct.
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Key Topics to Revise

1

Basic Concepts and Terminology

  • A random experiment is one whose outcome cannot be predicted in advance, even under identical conditions. Example: rolling a dice, flipping a coin.
  • A deterministic experiment always gives the same result under identical conditions. Example: verifying Ohm's law.
  • A trial is a single performance of a random experiment. Example: tossing a coin once.
2

Classical Approach to Probability

  • Classical probability is used when all outcomes in the sample space are equally likely.
  • The formula is: P(E) = Number of favourable outcomes / Total number of outcomes = n(E) / n(S).
  • The probability of any event E always satisfies: 0 ≤ P(E) ≤ 1.
3

Empirical (Experimental) Approach to Probability

  • Empirical probability is based on actual experiments and observations, not theoretical calculation.
  • It is also called 'relative frequency' or 'experimental probability'.
  • Formula: P(E) = r/n, where r = number of times event E occurred, n = total number of trials.
4

Types of Events

  • Equally Likely Events: Two or more events that have the same probability of occurring. Example: Getting Head or Tail when tossing a fair coin.
  • Sure (Certain) Event: An event that will definitely happen. P(E) = 1. Example: Getting a number between 1 and 6 when rolling a dice.
  • Impossible Event: An event that can never happen. P(E) = 0. Example: Getting 7 on a standard dice.

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Full Notes

Key Concepts

An experiment whose outcomes cannot beThe set of all possible outcomesAny subset of the sample spaceAlso called theoretical probabilityAlso called experimental or relative frequency

Frequently Asked Questions

What are the important topics in Probability for Tamil Nadu Board Class 9 Mathematics?
Key topics in Probability include Basic Concepts and Terminology, Classical Approach to Probability, Empirical (Experimental) Approach to Probability, Types of Events. Study these first, then practise questions on each for Class 9 exams.
How should I revise Probability for Class 9 exams?
Learn the core ideas first, then work through the 44 practice questions on Probability. Revise definitions regularly and use flashcards for quick recall before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

More resources for Probability

All Tamil Nadu Board Class 9 Mathematics Revision Notes

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