On 3/24/2013 3:50 AM, WM wrote: > On 24 Mrz., 02:30, Virgil <vir...@ligriv.com> wrote: > >> Given: that deleting anyone set from a union of sets does not decrease >> the union the set of remaining sets, >> >> THEN: Decreasing that union will require, if possible at all, deleting >> more than one member set, but deleting more than one member set still >> may not alsays decrease the union. >> >> Example: 100 different subsets each of 99 elements out of their union of >> 100 elements. Then the union of the set of any two or more of them >> equals the union of the set of all 100 of them. > > Enumerate the sets. Then there will be a first set that, when > subtracted from the union, will change the union of the remaining > sets. >
He is talking about the kind of "set" that every student in mathematics (except, perhaps, yours) learns about.
He is not talking about the theory of "monotonic-inclusive crayon marks".