MA.8.GR.1.6 · Geometric Reasoning
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.
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.
These come straight from Algebro's 8th grade pre-algebra question bank, easiest first. Answer one, check it, then move to the next.
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Showcase extra: the real practice and quiz players do not have this button.
Correct answer: C. 1,080°
Select every answer that applies, then check.
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Correct answer: A, C, D (highlighted above)
Enter the number only. Do not include units like $, %, or ft²
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Correct answer:
Showcase extra: the real practice and quiz players do not have this button.
Correct answer: A. 30°
Pick one match in each row, then check.
| 8 sides | 5 sides | 10 sides | 6 sides | |
|---|---|---|---|---|
| 108° | ||||
| 120° | ||||
| 135° | ||||
| 144° |
Showcase extra: the real practice and quiz players do not have this button.
Correct answer: shown by the green boxes above
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