﻿ Class 11 NCERT Math Solution
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TOPICS
Formulae
Events :-
```1. Impossible event : The empty set
2. Sure event: The whole sample space
3. Complementary event or ‘not event’ : The set A′ or S – A
4. Event A or B: The set A ∪ B
5. Event A and B: The set A ∩ B
6. Event A and not B: The set A – B
7. Mutually exclusive event: A and B are mutually exclusive if A ∩ B = φ
8. Exhaustive and mutually exclusive events: Events E1, E2,..., En are mutually exclusive and exhaustive if E1 ∪ E2 ∪ ...∪ En = S and Ei ∩ Ej = φ  V i ≠ j
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Probability of an event :-
```1. Probability of an event P(A) = n(A)/n(S), where n(A) = number of elements in the set A, n(S) = number of elements in the set S.
2. If A and B are any two events, then P(A or B) = P(A) + P(B) – P(A and B) equivalently, P(A ∪ B) = P(A) + P(B) – P(A ∩ B)
3. If A and B are mutually exclusive, then P(A or B) = P(A) + P(B)
4. If A is any event, then P(not A) = 1 – P(A)
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