Sum of interior angles
for 8th grade
Calculate the sum of the interior angles for each of the given polygons
Polygons: calculate the sum of interior angles from the number of sides
Any polygon with more than 3 sides can be split into a series of triangles by drawing lines between corners. Since we know that the interior angles of triangles sum to 180°, we can calculate the sum of the interior angles of any polygon by multiplying the number of triangles it contains by 180°. A shorthand version of this calculation is to take 2 away from the number of sides of a polygon and multiply that number by 180°.
The formula for calculating the sum of interior angles of a polygon given the number of sides is:
Sum of interior angles = (N - 2) x 180°
(where N = Number of sides and 180° = sum of interior angles of a triangle)
So, for any polygon with 5 sides (pentagon), the interior angles sum to:
3 x 180° = 540°
For a polygon with 10 sides (decagon), the interior angles sum to:
8 x 180° = 1440°
For a polygon with 3 sides (triangle), the interior angles sum to:
1 x 180° = 180°
Below is a table showing the first 8 question answer pairs for the topic "Sum of interior angles" as used in the lessons for this topic. Our games and tests for the topic use these 8 items plus 8 additional question answer pairs.
The topic "Sum of interior angles" is in the category Geometry & measures for 8th grade (ages 13 to 14).
Revise 'Sum of interior angles' with one of our games for 8th grade
Each of our math topics for secondary are made up of between 6 and 20 question and answer pairs (both the written form and a robot voice speaking those questions and answers). Each topic can be used with all the activities on the site.
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