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.

   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
2. 2.

   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
3. 3.

   Kira sketches a school roof end, a triangle with angles of 45° and 80°. The three corners fit along a straight line, which is 180°. What is the third angle, in degrees?

   55
4. 4.

   Luz sketches a boat sail, a triangle with angles of 60° and 80°. The three corners fit along a straight line, which is 180°. What is the third angle, in degrees?

   40
5. 5.

   Ren has glue and three craft sticks: 6 cm, 13 cm and 4 cm long. Laid end to end, the two shorter craft sticks reach 10 cm. Can the three craft sticks make a triangle?

   • No: the two shorter craft sticks together (10 cm) are not longer than the longest (13 cm)
   • No: a triangle needs all three craft sticks the same length
   • Yes: any three craft sticks make a triangle
6. 6.

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

   Ari has glue and three craft sticks: 9 cm, 5 cm and 6 cm long. Laid end to end, the two shorter craft sticks reach 11 cm. Can the three craft sticks make a triangle?

   • No: the craft sticks are all different lengths
   • Yes: the two shorter craft sticks together (11 cm) are longer than the longest (9 cm)
   • No: a triangle needs two craft sticks of the same length, and these craft sticks differ in length
8. 8.

   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)
9. 9.

   Noah labels triangle ABC on a map. Corner A is 30°, corner B is 70° and corner C is 80°. The longest side is across from the largest angle. Which side is the longest?

   • Side CA
   • Side AB
   • Side BC
10. 10.

    Ren labels triangle ABC on a map. Corner A is 40°, corner B is 85° and corner C is 55°. The longest side is across from the largest angle. Which side is the longest?

    • Side CA
    • Side BC
    • Side AB