# math

posted by
**sara** on
.

If A is a finite set and B is a proper subset of A, prove that |B| < |A|.

Hint: B is finite. What is the union of the disjoint sets B and A - B?

Note: |A| = size of A

posted by
**sara** on
.

If A is a finite set and B is a proper subset of A, prove that |B| < |A|.

Hint: B is finite. What is the union of the disjoint sets B and A - B?

Note: |A| = size of A