...is how spread out the numbers are
or
... is how spread out the numbers is
are or is and why?
Are; you are referring to a plural object-numbers.
. . . numbers are
The subject, numbers, is plural so a plural verb is needed.
In this case, the correct word to use is "are." Here's why:
The subject of the sentence is "numbers," which is plural. When the subject is plural, the corresponding verb should also be plural. In this case, the verb "to be" is being used, and its plural form is "are." Therefore, the correct sentence structure is:
"...is how spread out the numbers are."
Here's a general tip to help you determine which verb form to use:
If the subject of the sentence is singular (e.g., "the car," "the book"), you should use the singular form of the verb (e.g., "is"). If the subject is plural (e.g., "the cars," "the books"), you should use the plural form of the verb (e.g., "are").