← Triangles: angle sum, exterior angle and Pythagoras lesson New set →

Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 278 · 40 sums
TalentJR

The method (Inside 180, outside the sum): Angle sum: ∠A + ∠B + ∠C = 180°. Exterior angle = sum of the two interior opposite angles. Right-angled triangle: longest side² = side² + side² (3, 4, 5 and 5, 12, 13 are famous sets). Sides can make a triangle only if the two shorter sides add up to more than the longest side.

NameDateTime takenScore ___ / 40
  1. 1.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?
  3. 3.In triangle ABC, angle A = 81° and angle B = 64°. What is angle C (in degrees)?
  4. 4.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  5. 5.Can a triangle have sides of 3 cm, 3 cm and 5 cm? (a) Yes (b) No
  6. 6.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  7. 7.Can a triangle have sides of 9 cm, 19 cm and 12 cm? (a) Yes (b) No
  8. 8.Can a triangle have sides of 7 cm, 10 cm and 12 cm? (a) No (b) Yes
  9. 9.Can a triangle have sides of 1 cm, 6 cm and 6 cm? (a) No (b) Yes
  10. 10.The two interior opposite angles of a triangle are 58° and 24°. What is the exterior angle (in degrees)?
  11. 11.In triangle ABC, angle A = 27° and angle B = 96°. What is angle C (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 52° and 78°. What is the exterior angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 79° and angle B = 28°. What is angle C (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 59° and 22°. What is the exterior angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 58° and 44°. What is the exterior angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 33° and 63°. What is the exterior angle (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  22. 22.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  23. 23.An exterior angle of a triangle is 81°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 4 cm, 4 cm and 4 cm? (a) No (b) Yes
  27. 27.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  29. 29.Can a triangle have sides of 2 cm, 1 cm and 2 cm? (a) Yes (b) No
  30. 30.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 26° and angle B = 108°. What is angle C (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  34. 34.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  35. 35.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  36. 36.In triangle ABC, angle A = 67° and angle B = 86°. What is angle C (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 23° and 40°. What is the exterior angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?

Answer key

  1. 30
  2. 79
  3. 35
  4. 24
  5. Yes
  6. 40
  7. Yes
  8. Yes
  9. Yes
  10. 82
  11. 57
  12. 80
  13. 75
  14. 130
  15. 100
  16. 90
  17. 73
  18. 81
  19. 102
  20. 96
  21. 56
  22. 80
  23. 22
  24. 63
  25. 39
  26. Yes
  27. 41
  28. 72
  29. Yes
  30. 70
  31. 46
  32. 51
  33. 23
  34. 24
  35. 21
  36. 27
  37. 63
  38. 120
  39. 90
  40. 40

Free maths worksheets lessons, practice and worksheets at talentjr.in/maths-worksheets