**Goal:**To help students understand the addition and subtraction* properties of equality.

**Common Core Standard:**6.EE.4 - Identify when two expressions are equivalent (i.e., when the two expressions name the same number regardless of which value is substituted into them).

**ACOS Standard:**7.6.B.3 (2003); 6.15 (2010)

**Materials and Other Requirements:**1 deck of playing cards, 3-ring binder to serve as a partition, desk or table, two student volunteers

**Time Requirement**: 5-10 minutes

**Procedure:**Stand the 3-ring binder up on a table to serve as a partition. Position Student A and Student B on opposite sides of the partition. Give Student A a 3, a 5, and a 2 card. Give student B an 8 and a 2 card. Have them hold their cards so that the class can see them. Ask the class to state the sum of the cards Student A holds and then the sum of the cards Student B holds (10). Ask the class if the students are holding the same cards (

*NO*). Ask the class if the (values of the cards on the) two sides (of the partition) are equal (

*YES*). Tell students that for the remainder of the activity, the partition will stand in for an equal sign. Be sure that students recognize that the whole set-up (Student A, Student B, and the partition) is really an equation. Narrate as you hand Student A a 7 card. Ask the class if the two sides are equal now (

*NO*). Have the class explain why/how they know this (

*Student A's hand now adds up to 17 while Student B's hand is still 10*). Narrate as you hand Student B a 7 card. Ask if the two sides are equal now (

*YES*). Ask students to explain WHY the two sides are now equal (

*They both add up to 17).*If necessary, guide students towards the appropriate wording(

*If the sides start out equal, and we add the same number to both sides, the sides remain equal*or similar

*).*Repeat three or more times with different cards and different students.

**Closure:**Instruct the students to use inductive reasoning to write a rule about adding the same value to both sides of an equation. (If your students are not familiar with inductive reasoning, give a brief overview and then model using induction to write a rule.)

* Can easily be modified to show the subtraction property of equality, and with a little tweaking can be used to model the multiplication and division properties of equality.

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