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.

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

   77
2. 2.

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

   73
3. 3.

   Noah measures two angles of a triangular tent end: 26° and 84°. How many degrees is the third angle?

   70
4. 4.

   Bo builds an isosceles sail frame. The top angle is 100°. How many degrees is each base angle?

   40
5. 5.

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

   50
6. 6.

   Ren draws triangle GHQ and extends side GH past corner H. The outside angle at H is 118° and angle G is 47°. How many degrees is angle Q?

   71
7. 7.

   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
8. 8.

   Bo draws triangle CDF and extends side CD past corner D. Angle C is 50° and angle F is 60°. Which equation finds x, the outside angle at D?

   • x = 180 − 50 − 60
   • x = 50 + 60
   • x = 60 − 50
9. 9.

   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 = 38 + 51
   • x = 51 − 38
   • x = 180 − 38 − 51
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 = 64 + 41
    • x = 180 − 64 − 41