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.

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

   70
2. 2.

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

   58
3. 3.

   Jun builds an isosceles tent frame. Each base angle is 52°. How many degrees is the top angle?

   76
4. 4.

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

   104
5. 5.

   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
6. 6.

   Pia draws triangle YCD and extends side YC past corner C. Angle Y is 59° and angle D is 65°. How many degrees is the outside angle at C?

   124
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.

   Zee draws triangle WYC and extends side WY past corner Y. The outside angle at Y is 105° and angle W is 39°. How many degrees is angle C?

   66
9. 9.

   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
10. 10.

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