Multiple choice general knowledge math & puzzles

Given the mathematical set N of natural numbers (0, 1, 2, 3, 4, 5, ...) and the set Z of integer numbers (..., -3, -2, -1, 0, 1, 2, 3, 4, ...). Which of the following sentences is true?

  1. N has less numbers than Z

  2. N has as many numbers as Z

  3. N has more numbers than Z

  4. Indeterminable
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B Correct answer
Explanation

Both N (natural numbers) and Z (integers) are countably infinite sets with the same cardinality (aleph-null). A bijection exists between them: 0↔0, 1↔1, 2↔-1, 3↔2, 4↔-2, 5↔3, 6↔-3, etc., proving they have the same number of elements despite Z appearing 'larger'.

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