Let A and B be two independent events. Then which of following statements is not true?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → \( \bar{\mathrm{A}} \) and \( \bar{\mathrm{B}} \) are not independent.
If A and B are independent, then P(A ∩ B) = P(A) P(B), and so are the pairs \( \bar{A} \) and B, A and \( \bar{B} \), and \( \bar{A} \) and \( \bar{B} \). For the last pair:
\( P(\bar{A}\cap\bar{B})=1-P(A\cup B) \)
\( =1-P(A)-P(B)+P(A)P(B) \)
\( =(1-P(A))(1-P(B)) \)
\( =P(\bar{A})P(\bar{B}) \)
So \( \bar{A} \) and \( \bar{B} \) are independent, and Option (4), which says they are not, is the statement that is not true.
NCERT (2026-27 edition):
Independent Events

