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.

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

   73
3. 3.

   Pia looks at the side of a ramp, a right triangle. One of its other angles is 34°. How many degrees is the third angle?

   56
4. 4.

   Zee builds an isosceles roof frame. The top angle is 44°. How many degrees is each base angle?

   68
5. 5.

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

   50
6. 6.

   Milo draws triangle HQS and extends side HQ past corner Q. Angle H is 45° and angle S is 46°. How many degrees is the outside angle at Q?

   91
7. 7.

   Tala draws triangle SUV and extends side SU past corner U. The outside angle at U is 132° and angle S is 58°. How many degrees is angle V?

   74
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.

    Kira draws triangle GHQ and extends side GH past corner H. Angle G is 64° and angle Q is 41°. Which equation finds x, the outside angle at H?

    • x = 64 − 41
    • x = 180 − 64 − 41
    • x = 64 + 41