Question

Find the cardinal number of the following sets:
$A_2=\{x:x\in Nand3\le x<7\}$

Answer 1

Step : Find the cardinal number of the given set
Given: $A_2=\{x:x\in Nand3\le x<7\}$

As, $3\le x<7,x\in N$

$\Rightarrow x=3,4,5,6$

$\Rightarrow A_2=\{3,4,5,6\}$

Number of elements in set $A_2$ = 4

We know that the number of distinct element in a finite set is called its cardinal number.

Hence, the cardinal number of set $A_2$ is 4.