# Chairs and Plants

The number of chairs in a classroom is usually between 0 and 30. Let represent the number of chairs in a classroom, then we can say

Let’s be more precise. Unless there has been some kind of unusual interaction with the chairs, there are probably not say 10.25 chairs, even though 10.25 satisfies the inequality. We mean between 0 and 30, whole numbers only. Therefore

The letter-like-symbol is used for integers, that is, whole numbers.

On the other hand, if I am measuring an amaryllis plant that will grow to 60 cm, I can say that during its growth period it is is between zero and 60 cm.

In this case, it *can* be 10.25 cm. It will grow through all possible values. Let represent the height of an amaryllis plant in cm, and we can say

The letter-like-symbol is used for real numbers, that is, all numbers represented on a continuous number line from negative infinity to positive infinity.

# The Default

If you do not mention a particular set of numbers, we assume the set of real numbers.

# The four major number sets

In this course, you are expected to be familiar with Natural Numbers, Integers, Rational Numbers and Real Numbers. Click the image or the link to the mathisfun page to see them described more fully.