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.

   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
3. 3.

   Ari builds an isosceles tent frame. The top angle is 82°. How many degrees is each base angle?

   49
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.

   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
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.

   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 = 180 − 45 − 70
   • x = 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