Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Probability

Question:

Statement-1: Let n ≥ 3 and $A_1, A_2, ....A-n$ be n independent events such that $P(A_k)=\frac{1}{k+1}$ for 1 ≤ k ≤ n, then $P(\overline{A_1}∩ \overline{A_2}∩ \overline{A_3}∩ ......∩ \overline{A_n})=\frac{1}{n+1}$

Statement -2: Let $A_1, A_2, A_3, ........., A_n $ be n(≥ 3) events associated to a random experiment. Then $A_1, A_2, A_3, ........., A-n $ are independent if  $(A_1 ∩ A_2 ∩ ...........∩ A_n) = P(A_1)P(A_2)...P(A_n)$

1

Options:

Statement 1 is True, Statement 2 is true; Statement 2 is a correct explanation for Statement 1.

Statement 1 is True, Statement 2 is True; Statement 2 is not a correct explanation for Statement 1.

Statement 1 is True, Statement 2 is False.

Statement 1 is False, Statement 2 is True.

Correct Answer:

Statement 1 is True, Statement 2 is False.

Explanation:

We know that three or more events associated to a random experiment are independent iff they are pairwise independent as well as as independent together. So, statement-2 is not true.

If $P(A_k)=\frac{1}{k+1}$ for $ k=1,2,.....,n$ and $ A_1, A_2, ......A_n$ are independent, then 

$P(\overline{A_1}∩ \overline{A_2}∩ ......∩ \overline{A_n})= P(\overline{A_1}P(\overline{A_2})....P(\overline{A_n})$

$⇒ P(\overline{A_1}∩ \overline{A_2}∩ ......∩ \overline{A_n})=\frac{1}{2}×\frac{2}{3}×\frac{3}{4}×....×\frac{n}{n+1}=\frac{1}{n+}$

So, statement-2 is true.