The Integers · Example 1

Which of the following are integers and which are not?

$$\begin{array}{cc}\text{−3}& \text{Is an integer, as it is the negative of a counting number}\\ \sqrt{24}& \text{This is not written as an integer. Entering the square root of 24 in a calculator, such as desmos, the result is 4.899 (rounded off). Since this is not an integer, then }\sqrt{24}\text{ is not an integer.}\\ \text{36/4}& \text{Since 36 divided by 4 is 9, and 9 is an integer, then 36/4 is an integer.}\\ \text{45}& \text{Is an integer, as it is a counting number}\\ \text{63.9}& \text{Is not an integer, because it is not a counting number and not the negative of a counting number.}\\ \text{2/7}& \text{Dividing 2 by 7 results in a number less than 1, but greater than 0, so is between two consecutive integers. So, 2/7 is not an integer.}\\ \text{−16.0}& \text{Is an integer, since the decimal part is 0}\end{array}$$

Its source prints no answer for this problem, so there's nothing to check against.

OpenStax, Contemporary Mathematics · §3.2 The Integers · Example 1