Let a be the common cardinality of sets A and C. Let b be the size of B. If C is a subset of B, then a<= b. I understand why this is true, but how do I give a solid proof? Thanks.
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Originally Posted by jzellt Let a be the common cardinality of sets A and C. Let b be the size of B. If C is a subset of B, then a<= b. I understand why this is true, but how do I give a solid proof? Thanks. note that if $\displaystyle C \subseteq B$, then $\displaystyle |C| \le |B|$ (you can prove this by contradiction). here, since $\displaystyle |A| = |C|$, we have $\displaystyle |A| \le |B|$
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