A number $\mathrm{n}$ is chosen at random from $s=\{1,2,3, \ldots, 50\}$. Let $\mathrm{A}=\{n \in s: n$ is a…

A number $\mathrm{n}$ is chosen at random from $s=\{1,2,3, \ldots, 50\}$. Let $\mathrm{A}=\{n \in s: n$ is a square $\}$, $\mathrm{B}=\{n \in s: n$ is a prime $\}$ and $\mathrm{C}=\{n \in s: n$ is a square $\}$. Then, correct order of their probabilities is
  1. $p(A) < p(B) < p(C)$
  2. $p(A)>p(B)>p(C)$
  3. $p(\mathrm{~B}) < p(A) < p(C)$
  4. $p(A)>p(c)>p(B)$

Solution

Given, $S=\{1,2,3 \ldots, 50\}$ $\begin{aligned} A & +\left\{n \in S: n+\frac{50}{n}>27\right\} \\ & =\left\{n \in S: n^2-27 n+50>0\right\} \\ & =\{n \in S:(n-25)(n-2)>0\} \\ & =\{n \in S: n < 2 \text { or } n>25\} \\ & =\{1,26,27,28, \ldots, 50\} \end{aligned}$ $\begin{aligned} & \Rightarrow n(A)=26 \\ & B=\{n \in S: n \text { is prime }\} \\ & =\{2,3,5,7,11,13,17,19,23 \text {, } \\ & 29,31,37,41,43,47\} \\ & \Rightarrow n(B)=15 \\ & C=\{n \in S: n \text { is a square }\}=\{1,4,9,16,25,36,49\} \\ & \Rightarrow n(C)=7 \\ & \therefore \quad p(A)=\frac{n(A)}{n(S)}=\frac{26}{50} \text {, } \\ & \Rightarrow \quad p(B)=\frac{n(B)}{n(S)}=\frac{15}{50} \text {, } \\ & p(C)=\frac{n(C)}{n(S)}=\frac{7}{50} \\ & \therefore \quad p(A)>p(B)>p(C) \\ & \end{aligned}$

Asked in: TEST SERIES MHT-CET Full Test 6

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