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### Unit 9: Lesson 1

A quadrilateral is a polygon with 4 sides.
A shape with 4 sides and no right angles. The opposite sides are parallel. Each side is labeled 5 centimeters.
A shape with 4 sides. The left and right sides are parallel. The top side is labeled 3 centimeters, the bottom side is labeled 5 centimeters, the left side is labeled 4 centimeters, and the right side is labeled 6 centimeters.

## What are some common types of quadrilaterals?

Some common types of quadrilaterals include squares, rectangles, rhombuses, and trapezoids.

## What is the difference between a square and a rectangle?

A square has four sides that are all the same length, while a rectangle has two sets of two sides that are the same length.
A square is always is a rectangle but a rectangle is not a square.

## What is a right angle?

A right angle is a type of angle that looks like the corner of a square. When two lines meet at a right angle, they form a 90 degree angle.
One way to tell if an angle is a right angle is to use a tool called a protractor to measure it. Another way is to use a right angle ruler or "square" to see if the two lines line up perfectly with the tool.