Question

What is the cardinal number of the set A = {Letters of the word APPLE}.

Answer 1

Given,
A = {Letters of the word APPLE}
$\Rightarrow$ A = {A, P, L, E}

($\because$ While listing the elements of a set, we do not repeat any element.)

$\Rightarrow n\left(A\right)=4$
$\therefore$ The cardinal number of the given set $A$ is 4.