CCSS Math: 3.G.A.1
Classify quadrilaterals, including rectangles, rhombuses, and squares.

A quadrilateral is a polygon with four sides.

### Study some examples

Here are some examples of quadrilaterals:

### Try it yourself

Which of the following shapes are quadrilaterals?
The following shapes are quadrilaterals because they are polygons with four sides. Remember: polygons must be closed figures.

Some quadrilaterals go by special names like rectangle, rhombus, and square. Let's learn about them!

# Rectangles

What makes a shape a rectangle?
• There are four right angles.
• There are four sides because it's a quadrilateral.

### Study some examples

Here are some examples of rectangles:

### Try it yourself

Which of the following shapes are rectangles?
The following shapes are rectangles because they are quadrilaterals with four right angles. Remember: quadrilaterals must have four sides.*

### Challenge problem

Let's consider one more shape:
Does the shape have four right angles?
So, is the shape a rectangle?
That's right!
A rectangle is a quadrilateral with four right angles.
Squares are quadrilaterals. Squares have four right angles.
So, squares are rectangles!

# Rhombuses

What makes a shape a rhombus?
• All sides are the same length.
• There are four sides because it is a quadrilateral.

### Study some examples

Here are some examples of rhombuses:
Yes, it is!
A rhombus is a quadrilateral with all sides of equal length.
Squares are quadrilaterals. Squares have all sides of equal length.
So, squares are rhombuses!

### Try it yourself

Which of the following shapes are rhombuses?
The following shapes are rhombuses because they are quadrilaterals with all sides of equal length:

# Squares

What makes a shape a square?
• All sides are of equal length.
• There are four right angles.
• There are four sides because it's a quadrilateral.

### Study some examples

Here are some examples of squares:

### Try it yourself

Which of the following shapes are squares?
The following shapes are squares because they are quadrilaterals with four right angles and all sides of equal length:

# Challenge question 1

Drag the points to create a shape that is both a rectangle and a rhombus.
A $\blueD{\text{rectangle}}$ is a quadrilateral with $\blueD{\text{four right angles}}$.
A $\greenD{\text{rhombus}}$ is a quadrilateral with $\greenD{\text{all sides of equal length}}$.
A square is a quadrilateral with $\blueD{\text{four right angles}}$ and $\greenD{\text{all sides of equal length}}$.
So, a square is a $\blueD{\text{rectangle}}$ and a $\greenD{\text{rhombus}}$.
The solution is to draw a square.

# Challenge question 2

Which of the following describe this shape?
A quadrilateral is a four-sided polygon. Is this shape a four-sided polygon? Yes!
A rectangle is a quadrilateral with four right angles. Does this shape have four right angles? Yes!
A rhombus is a quadrilateral with all sides of equal length. Does this shape have all sides of equal length? Yes!
A square is a four-sided polygon with four right angles and all sides of equal length. Is this shape a square? Yes!
So, the shape is a quadrilateral, rectangle, rhombus, and square!