## Thinking Mathematically (6th Edition)

$2 \div 3 = \frac{2}{3}$ ,which is not a natural number. Thus, the natural numbers are not closed with respect to division.
RECALL: The natural numbers are $1, 2, 3, ...$. Note that $2 \div 3 = \frac{2}{3}$, which is not a natural number. Thus, the natural numbers are not closed with respect to division.