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Section 10: Problem 3 Solution

Working problems is a crucial part of learning mathematics. No one can learn topology merely by poring over the definitions, theorems, and examples that are worked out in the text. One must work part of it out for oneself. To provide that opportunity is the purpose of the exercises.
James R. Munkres
Both and are well-ordered in the dictionary order. Do they have the same order type?
No, the first set has an element which is not the smallest element of the set but has no immediate predecessor, while the second set does not have such an element (therefore, there is no order preserving bijection, as if there is, say , then cannot be the smallest element, hence, it must have a predecessor , but then , that is , and ).