This module establishes equivalence of sets by a one-to-one exchange of objects. E.g. Upsetting equivalence (destroying conservation of numbers) by adding one object to a set, or taking one away. This helps introduce vocabulary for comparing quantity: more, less, the same, as many as, etc. Clauses of implication (condition statements) can be introduced as well: If there is one penny for every toy, then there are as many pennies as toys. Teacherís guide included.