Angles of a triangle: the sum and the exterior angle

Answer Key - Grade 8 Math Worksheet

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

1. 1.

   Kira measures two angles of a triangular roof truss: 31° and 52°. How many degrees is the third angle?

   97
2. 2.

   Luz measures two angles of a triangular sail: 46° and 57°. How many degrees is the third angle?

   77
3. 3.

   Milo measures two angles of a triangular ramp side: 38° and 69°. How many degrees is the third angle?

   73
4. 4.

   Ren leans a ladder on a wall, making a right triangle with the ground. One of its other angles is 75°. How many degrees is the third angle?

   15
5. 5.

   Tala cuts a right triangle from paper. One of its other angles is 32°. How many degrees is the third angle?

   58
6. 6.

   Esme builds an isosceles roof frame. Each base angle is 65°. How many degrees is the top angle?

   50
7. 7.

   Kira builds an isosceles sail frame. Each base angle is 38°. How many degrees is the top angle?

   104
8. 8.

   Ari draws triangle DFG and extends side DF past corner F. The outside angle at F is 141° and angle D is 63°. How many degrees is angle G?

   78
9. 9.

   Esme draws triangle WYC and extends side WY past corner Y. Angle W is 45° and angle C is 70°. Which equation finds x, the outside angle at Y?

   • x = 70 − 45
   • x = 45 + 70
   • x = 180 − 45 − 70
10. 10.

    Jun draws triangle UVW and extends side UV past corner V. Angle U is 38° and angle W is 51°. Which equation finds x, the outside angle at V?

    • x = 180 − 38 − 51
    • x = 38 + 51
    • x = 51 − 38