# Algebra Tiles

Look at the section on Number to Algebra for ideas on how to introduce Algebra Tiles.

### Expressions with algebra tiles

This activity introduces expressions with unknown variables and constant terms. Ask students to match the models to the statements. Ideally they should already be familiar with base blocks and algebra tiles.

Next move the change x slider above to show that x is variable and the units are constant. The expressions can be manipulated using Mathsbot to highlight the distributive property 2(x+3) = 2x + 6.

Using the rectangle representation links to the area model for multiplication and division and highlights the common factor of 2. ### Equal expressions

Move the slider to change the value of x. When does 3x + 2 = x + 6?

When is 3x+2 > x+6?

When is 3x+2 < x+6?

### Algebra tiles and graphs

Making connections between the bar model and the graph model.

Change the number bars, size of constant term and position using the sliders.

### Compare expressions

Compare 3x and x+3

Change the value of x by moving the sliders

### Equations and graphs

Solve equations and inequalities by moving the slider and comparing the bar model to the graph.

### Solving Linear Equations Algebra tiles do not show equality and inequality.

Before using algebra tiles to solve equations represent equality and inequality using a bar model or a dynamic model like equal expressions above. ### Balance/elimination method  Add multiples of x’s, -x’s, 1’s or -1’s to both expressions to isolate x on one side of the equation.

This method will always work and leads to the standard balancing method. 3 - x + x = x - 4 + x

3 + 4 = 2x - 4 + 4

### Simultaneous Equations

Change x and y until the bars are equal.

### Simultaneous equations by elimination

The elimination method is clear to see using algebra tiles and zero pairs when the coefficients have opposite signs. 2x + y = 7

x - y = 2

Add the two equations together to get the image below. 3x + y - y = 9

The zero pair highlights the elimination. 3x = 9

x = 3 Substitute into 2x + y = 7

6 + y = 7

y = 1

x = 3 and y = 1

From here you can move on to multiplying one and then both equations before eliminating by adding the equations.

Difficulties and misconceptions start when the coefficients are the same sign.

### Method 1 – subtracting the two equations or finding the difference ### Method 2 – elimination using zero pairs Method 2 also avoids the difficulties that arise in questions that involve subtracting negatives.  