Constructing relationships based on quantity requires a firm understanding of cardinality, order, and conservation of number. In order to compare two quantities, a student must first be able to name the amount in each set of objects. Cardinality is knowing that the last number stated when counting a set of objects also represents the total number of items in the set.

When comparing two quantities, students must be able to correctly identify the number of each quantity. Students must also be able to order quantities so they can accurately identify the larger or smaller amount, as defined by stable order count. Finally, conservation of number is crucial in students' ability to acknowledge the relationship of the two sets. For instance, conservation of number is knowing that a quantity of objects that is spread out is the same quantity of objects closely arranged in a line as illustrated below:

Both rows of cars represent the same quantity even though the second row appears to take up more space. Conservation of number enables students to make judgments about quantity based on the number of objects rather than the arrangement of the objects.