Question

What is the cardinality of each of these sets? a) {a} b) {{a}} c) {a, {a}} d) {a, {a}, {a, {a}}}

Answer 1

Cardinality of a finite set is the number of elements in it.

There is 1 element in {a}, 1 element in {{a}}, 2 elements in {a, {a}}, 3 elements in {a, {a}, {a, {a}}}.

Thus:

a) 1

b) 1

c) 2

d) 3