Nested sets

#IE#nested#specific

Statement

If $A\subseteq B\subseteq C$ with $|A|=3$ , $|B|=7$ , $|C|=10$ , compute $|A\cup B\cup C|$ .

Hint

Union of nested sets is the largest set.

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Union. $A\cup B\cup C=C$ , so $|A\cup B\cup C|=10$ .

Conclusion. $|A\cup B\cup C|=10$ .