In this lesson, students practice finding simpler, equivalent equations in order to solve for an unknown. In the row game, students notice that multiplying an equation by a number results in the same answer for the unknown. In the other activity, students follow a plan to determine the weights of two different items by finding the weights of different groupings and combining their weights.
Students use tools strategically (MP5) if they choose to manipulate physical items to represent the items being weighed in the second activity. Students reason abstractly and quantitatively (MP2) when they find the ways to create the appropriate groupings to solve for the weight of a single item.
Lesson overview
 15.1 Warmup: Estimation: Coin Weight (5 minutes)
 15.2 Activity: Row Game: Equations (15 minutes)
 15.3 Activity: What Were They Thinking (20 minutes)
Learning goals:
 Recognize that a multiple of an equation has the same solution as the original equation.
 Use a concrete example to recognize moves that can be done to a system of equations without changing the solution.
Learning goals (student facing):
 Let’s study solutions and nonsolutions.
Required materials:
 Coins
 Number cubes
Required preparation:

Provide access to two different types of items to represent nickels, dollar coins, plastic bricks, and number cubes.
Standards:
 This lesson builds towards the standards: CCSS.HSAREI.C.5MS.AREI.5CCSS.HSAREI.C.6MS.AREI.6MO.A1.REI.B.5MO.A1.REI.B.3
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