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Problem #14 · August 10, 2026

Natural numbers

Which of the following numbers is not a natural number?
  1. A00
  2. B11
  3. C77
  4. D1515
  5. E102102

WORKED EXAMPLE

Solution

Natural numbers are the numbers 1,2,3,…1, 2, 3, \ldots used for counting objects. 00 is not a counting number, so it does not belong to the set of natural numbers (N\mathbb{N}); all the other given numbers are natural numbers.
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