Chapter 11, Problem 18CT

To determine

To calculate: to find the probability that for first presentation is not mine.

Answer to Problem 18CT

the probability that for first presentation is not mine is $1-\frac{1}{25!}$ .

Explanation of Solution

Given information : consider, thedataprovided in the question,

total students = $25$

Formula used: $P{}_r=\frac{n!}{\left(n-r\right)!}$

Calculation : to find the probability, first find the total number of possibilities,

Take all five projects so that is equal to

  $\begin{array}{l}P{}_r=\frac{n!}{\left(n-r\right)!}\\ P{}_{25}=\frac{25!}{\left(25-25\right)!}\\ P{}_{25}=\frac{25!}{0!}\\ P{}_{25}=25!\end{array}$

Now find the probability that first I selected,

Probability = $\frac{1}{25!}$

Now if I am not the first so the probability = $1-\frac{1}{25!}$

Hence,

Thus,the probability that for first presentation is not mine is $1-\frac{1}{25!}$ .