Which property states that the grouping of numbers does not affect the sum?

The property that states that the grouping of numbers does not affect the sum is the associative property. This property allows you to change the grouping of numbers when adding, without changing the result. For example, when you add the numbers 2, 3, and 4, you can calculate it as (2 + 3) + 4 or 2 + (3 + 4), and both will yield the same sum of 9.

This demonstrates that the way in which numbers are grouped does not influence the outcome of the addition operation, reinforcing the idea that addition is associative. Understanding this property helps with simplifying calculations in more complex mathematical expressions.