Chapter 5 - Number Theory and the Real Number System - 5.5 Real Numbers and Their Properties; Clock Addition - Exercise Set 5.5 - Page 309: 46

$1 \div 4 = \frac{1}{4}$ 1 and 4 are natural numbers, but $\frac{1}{4}$ is not.

RECALL: Natural numbers are the counting numbers 1, 2, 3, ... Natural numbers are not closed with respect to division, as can be seen in the example below: 1 and 4 are natural numbers. However, $1 \div 4 = \frac{1}{4}$, which is not a natural number.