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 A set S contains 7 elements. A non-empty subset A of S and an element x of S are chosen at random. Then the probability that x\epsilon A is :

Option: 1

\frac{1}{2}


Option: 2

\frac{64}{127}


Option: 3

\frac{63}{128}


Option: 4

\frac{31}{128}


Answers (1)

best_answer

As learnt in concept

Probability of occurrence of an event -

Let S be the sample space then the probability of occurrence of an event E is denoted by P(E) and it is defined as 

P\left ( E \right )=\frac{n\left ( E \right )}{n\left ( S \right )}

P\left ( E \right )\leq 1

P(E)=\lim_{n\rightarrow\infty}\left(\frac{r}{n} \right )

 

 

- wherein

Where n repeated experiment and E occurs r times.

 

 First we find subsets of A=2^{7}-1

=127

Number of subsets of s which contain x is 2^{6}

Prob=\frac{2^{6}}{2^{7}-1}

=\frac{64}{127}

Posted by

vinayak

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