Question

What is the cardinal number of the following sets?

The set of months of the years with names that begin with the letter $S$

Answer 1

The number of distinct elements in a finite set is called the cardinal number of the set. It is denoted by $n\left(A\right)$

Given set:

The set of months of the years with names that begin with the letter $S$

Name of the month of the year start with letter $S$ is $A=\left\{September\right\}$

It can be seen the set contains only one month.

Therefore, the Cardinal number of the set of months of the years with names that begin with the letter $S$ is $n\left(A\right)=1$