Answer
The size of a class is a natural number.
Work Step by Step
The set of natural numbers is { 1, 2, 3, 4, 5, ... } .
The set of whole numbers is { 0, 1, 2, 3, 4, 5, ... }
The set of integers is {... , -4, -3, -2, -1,0, 1, 2, 3, 4,...}
The set of rational numbers$: \displaystyle \frac{a}{b},\ b\neq 0$, and b integers
Irrational numbers: are not rational (can not be written as $\displaystyle \frac{a}{b},\ b\neq 0$)
Real numbers: all rational and irrational numbers.
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We count the number of students when we determine the size of a class.
If there are no students, there is no class.
The numbers used for counting are natural numbers, { 1, 2, 3, 4, 5, ... }
The size of a class is a natural number.
