Angles and sides of triangles

Answer Key - Grade 6 Math Worksheet - Building Confidence

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

1. 1.

   Ari sketches a boat sail, a triangle with angles of 50° and 60°. The three corners fit along a straight line, which is 180°. What is the third angle, in degrees?

   70
2. 2.

   Bo sketches a tent flap, a triangle with angles of 40° and 75°. The three corners fit along a straight line, which is 180°. What is the third angle, in degrees?

   65
3. 3.

   Esme sketches a tower roof end, a triangle with angles of 35° and 45°. The three corners fit along a straight line, which is 180°. What is the third angle, in degrees?

   100
4. 4.

   Jun sketches a castle pennant: a triangle with angles of 20° and 55°. The three corners fit along a straight line, which is 180°. What is the third angle, in degrees?

   105
5. 5.

   Milo sketches a tent flap, a triangle with angles of 70° and 65°. The three corners fit along a straight line, which is 180°. What is the third angle, in degrees?

   45
6. 6.

   Pia has glue and three craft sticks: 10 cm, 2 cm and 5 cm long. Laid end to end, the two shorter craft sticks reach 7 cm. Can the three craft sticks make a triangle?

   • No: a triangle needs all three craft sticks the same length
   • Yes: any three craft sticks make a triangle
   • No: the two shorter craft sticks together (7 cm) are not longer than the longest (10 cm)
7. 7.

   Tala has glue and three craft sticks: 3 cm, 8 cm and 5 cm long. Laid end to end, the two shorter craft sticks reach 8 cm. Can the three craft sticks make a triangle?

   • No: a triangle needs all three craft sticks the same length
   • No: the two shorter craft sticks together (8 cm) are not longer than the longest (8 cm)
   • Yes: the two shorter craft sticks reach 8 cm, as far as the longest, so they fit and a triangle forms
8. 8.

   Zee has glue and three craft sticks: 10 cm, 4 cm and 6 cm long. Laid end to end, the two shorter craft sticks reach 10 cm. Can the three craft sticks make a triangle?

   • Yes: the two shorter craft sticks reach 10 cm, as far as the longest, so they fit and a triangle forms
   • No: a triangle needs all three craft sticks the same length
   • No: the two shorter craft sticks together (10 cm) are not longer than the longest (10 cm)
9. 9.

   Bo has glue and three craft sticks: 8 cm, 4 cm and 7 cm long. Laid end to end, the two shorter craft sticks reach 11 cm. Can the three craft sticks make a triangle?

   • No: a triangle needs two craft sticks of the same length, and these craft sticks differ in length
   • No: the craft sticks are all different lengths
   • Yes: the two shorter craft sticks together (11 cm) are longer than the longest (8 cm)
10. 10.

    Pia labels triangle ABC on a map. Corner A is 100°, corner B is 50° and corner C is 30°. The longest side is across from the largest angle. Which side is the longest?

    • Side CA
    • Side AB
    • Side BC