Chapter 14 · Question 5

State and use the complement rule. If P(E)=35P(E)=\frac35, find P(not E)P(\text{not }E).

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Q5

State and use the complement rule. If P(E)=35P(E)=\frac35, find P(not E)P(\text{not }E).

Answer Revealed
Direct Answer:
The complement rule is P(E)+P(E)=1P(E)+P(\overline E)=1. So P(E)=135=25P(\overline E)=1-\frac35=\frac25.

Simple Explanation

The event and its complement together cover all outcomes, so their probabilities add to 1.

Exam-Ready Structure

For any event EE, not EE is denoted E\overline E. Since either EE happens or it does not, P(E)+P(E)=1P(E)+P(\overline E)=1. Thus P(E)=1P(E)=135=25P(\overline E)=1-P(E)=1-\frac35=\frac25.

Key Points

  • The complement rule is P(E)+P(E)=1P(E)+P(\overline E)=1.
  • Use the NCERT formula or theorem carefully.
  • Write units and final conclusion where applicable.