Angles of a polygon: add up the triangles

Answer Key - Grade 8 Math Worksheet

Circle the best answer, or write your answer on the line.

1. 1.

   Jun measures every inside angle of a 9-sided paper cut-out and adds them up. What should the total be, in degrees?

   1260
2. 2.

   Kira measures every inside angle of a 10-sided shape drawn on paper and adds them up. What should the total be, in degrees?

   1440
3. 3.

   Luz measures every inside angle of a 12-sided shape cut from paper and adds them up. What should the total be, in degrees?

   1800
4. 4.

   Milo draws a regular octagon shape drawn on paper (8 equal sides and angles). All its inside angles are equal. How many degrees is each one?

   135
5. 5.

   Noah draws a regular 9-sided paper shape. All its inside angles are equal. How many degrees is each one?

   140
6. 6.

   Pia draws a regular 12-sided paper cut-out. All its inside angles are equal. How many degrees is each one?

   150
7. 7.

   Ren draws a regular 20-sided shape drawn in crayon. All its inside angles are equal. How many degrees is each one?

   162
8. 8.

   Tala's hexagon paper cut-out has five angles of 120°, 135°, 112°, 128° and 117°. What is the sixth angle, in degrees?

   108
9. 9.

   Ari's hexagon shape drawn on paper has five angles of 150°, 102°, 124°, 116° and 131°. What is the sixth angle, in degrees?

   97
10. 10.

    Bo's hexagon shape cut from paper has five angles of 108°, 144°, 127°, 99° and 136°. What is the sixth angle, in degrees?

    106