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MA.8.GR.1.6 · Geometric Reasoning

Interior Angle Sums of Polygons: Sample FAST Questions

Splitting a regular polygon into triangles from a single vertex produces n − 2 triangles, so the interior angles sum to (n − 2) × 180 degrees. 8th graders derive the formula by decomposition and then use it on pentagons, hexagons, octagons, and larger polygons.

How the FAST tests this benchmark

FAST items are equation editor questions for an angle sum or a single interior angle, plus multiple choice items on polygons named by their side count. For a regular polygon, one angle is the sum divided by n, and skipping that last division is the common miss.

Skills students need

  • Decompose a polygon into triangles
  • Use (n − 2) × 180 to find an interior angle sum
  • Find one interior angle of a regular polygon
  • Work backward from an angle sum to the number of sides

Try 6 real MA.8.GR.1.6 questions

These come straight from Algebro's 8th grade pre-algebra question bank, easiest first. Answer one, check it, then move to the next.

Question 1 of 6

Answer it and Algebro checks it instantly

Question 1EasyMultiple Choice
A gazebo has a floor shaped like a regular octagon (8 sides). What is the sum of the measures of its interior angles?

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More 8th grade geometric reasoning benchmarks

MA.8.GR.2.1

Identifying Translations, Reflections, and Rotations

MA.8.GR.2.2

Finding the Scale Factor of a Dilation

MA.8.GR.2.3

Transformations on the Coordinate Plane

MA.8.GR.1.6: Polygon Angle Sums Practice | Algebro