Unit 1, Lesson 11
Polygons
Grade 6
11.1
Warm-up
Which Three Go Together: Triangles
Which three go together? Why do they go together?
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Which three go together? Why do they go together?
These five figures are polygons.
The next six figures are not polygons.
Circle the figures that are polygons.
What do the figures you circled have in common? What characteristics helped you decide whether a figure was a polygon?
Find the area of two quadrilaterals of your choice. Show your reasoning.
Find the area of the shaded region in square units. Show your reasoning.
A polygon is a two-dimensional figure composed of straight line segments.
Here is a polygon with 5 sides. The vertices are labeled
A polygon encloses a region. The area of a polygon is the area of the region inside it.
We can find the area of a polygon by decomposing the region inside it into triangles and rectangles.
The first two diagrams show the polygon decomposed into triangles and rectangles. The sum of their areas is the area of the polygon. The last diagram shows the polygon enclosed with a rectangle. Subtracting the areas of the triangles from the area of the rectangle gives us the area of the polygon.
A polygon is a closed, two-dimensional shape with straight sides that do not cross each other.
Figure
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