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Polygon Interior Angles

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Polygon Interior Angles

Show your working for calculation questions. Give angle answers in degrees.

Using the interior-angle sum

1.Find the sum of the interior angles of a triangle.
2.Find the sum of the interior angles of a quadrilateral.
3.Find the sum of the interior angles of a pentagon.
4.Find the sum of the interior angles of a hexagon.
5.Which polygon has an interior-angle sum of 1,260°?
  • Heptagon
  • Octagon
  • Nonagon
  • Decagon
6.Calculate the sum of the interior angles of a 14-sided polygon. Show your working.

Finding unknown angles

7.Three interior angles of a quadrilateral are 78°, 104° and 91°. Find its fourth interior angle.
8.Four interior angles of a pentagon measure 101°, 116°, 94° and 128°. Calculate the fifth angle.
9.A hexagon has five interior angles of 117°, 124°, 109°, 132° and 121°. What is the sixth angle?
  • 117°
  • 127°
  • 137°
  • 147°
10.A heptagon has six interior angles of 130°, 140°, 125°, 138°, 132° and 135°. Find the seventh angle.

Reasoning and regular polygons

11.A regular polygon has interior angles of 150° each. How many sides does it have?
12.A regular polygon has an interior-angle sum of 1,440°. Find its number of sides and the size of each interior angle.
13.True or false: increasing a polygon's number of sides by one increases its interior-angle sum by 180°.
TrueFalse
14.A student says a regular polygon with an interior angle of 160° must have 18 sides. Check the claim and give the correct number of sides, showing why.
15.Match each polygon to its interior-angle sum.
  • Octagon (8 sides)
  • Decagon (10 sides)
  • Dodecagon (12 sides)
  • Nonagon (9 sides)
  • 1,260°
  • 1,080°
  • 1,440°
  • 1,800°

3 printable pages

  • Polygon Interior Angles, page 1 of 3: Using the interior-angle sum

    Page 1

  • Polygon Interior Angles, page 2 of 3: Finding unknown angles, Reasoning and regular polygons

    Page 2

  • Polygon Interior Angles, page 3 of 3: 14. A student says a regular polygon with an interior angle of 160° must have 18 sides.…

    Page 3

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