Take the set of positive integers plus 0 and the subset of all positive integers ending in, say 5. I see no reason why there can't be a one to one correspondence between the subset and the set. Am I wrong? (I have been challenged on this assertion.)(adsbygoogle = window.adsbygoogle || []).push({});

EDIT: The challenge was: The subset is a proper subset and a proper subset cannot have a one to one mapping to its set. I agree this would be true for finite sets.

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# Correspodance between infinite sets

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