Grade 8 · Geometry & measurement

Polygon angle formulas practice

Polygon angle formulas is a grade 8 math skill aligned to Common Core standard 8.G.A.5: use informal arguments to establish facts about the angle sum and exterior angle of triangles, and about the angles created when parallel lines are cut by a transversal. Below are 8 practice questions with answers and step-by-step explanations, drawn from the 15 polygon angle formulas problems our math games drill.

CCSS 8.G.A.515 questions in the bank
Sample questions

Try 8 for free

Question 1easy

What is the sum of the interior angles of a triangle?

The interior angle sum of a triangle is 180°180°.

Question 2easy

What is the sum of the interior angles of a quadrilateral?

The interior angle sum of a quadrilateral is 360°360°.

Question 3easy

What is the sum of the interior angles of a pentagon?

A pentagon has 55 sides: (5−2)×180=540°(5-2) \times 180 = 540°.

Question 4easy

What is the sum of the interior angles of a hexagon?

A hexagon has 66 sides: (6−2)×180=720°(6-2) \times 180 = 720°.

Question 5easy

What is the sum of the interior angles of a heptagon?

A heptagon has 77 sides: (7−2)×180=900°(7-2) \times 180 = 900°.

Question 6easy

What is the sum of the interior angles of a octagon?

A octagon has 88 sides: (8−2)×180=1080°(8-2) \times 180 = 1080°.

Question 7easy

What is the sum of the interior angles of a nonagon?

A nonagon has 99 sides: (9−2)×180=1260°(9-2) \times 180 = 1260°.

Question 8easy

What is the sum of the interior angles of a decagon?

A decagon has 1010 sides: (10−2)×180=1440°(10-2) \times 180 = 1440°.

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Math games for Grade 8

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Tests that cover polygon angle formulas:
NAEPSBACPSAT 8/9SC READYNC EOG/EOC
More Grade 8 skills:
Linear coefficient interpretationsGraphing linear equationsModeling linear situationsPythagorean theoremScatter plots and bivariate dataScatterplots and trend linesDistance formulaExponent rulesAll Grade 8 practice →

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