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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 865 · 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 triangle ABC, angle A = 60° and angle B = 24°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  3. 3.An exterior angle of a triangle is 123°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  4. 4.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  5. 5.Can a triangle have sides of 11 cm, 9 cm and 5 cm? (a) No (b) Yes
  6. 6.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  7. 7.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  8. 8.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  9. 9.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  10. 10.In triangle ABC, angle A = 36° and angle B = 34°. What is angle C (in degrees)?
  11. 11.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  12. 12.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  15. 15.Can a triangle have sides of 10 cm, 2 cm and 9 cm? (a) Yes (b) No
  16. 16.The two interior opposite angles of a triangle are 51° and 21°. What is the exterior angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  18. 18.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  19. 19.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  20. 20.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  21. 21.Can a triangle have sides of 11 cm, 12 cm and 7 cm? (a) No (b) Yes
  22. 22.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  24. 24.Can a triangle have sides of 5 cm, 14 cm and 9 cm? (a) No (b) Yes
  25. 25.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  28. 28.In triangle ABC, angle A = 47° and angle B = 65°. What is angle C (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 42° and 24°. What is the exterior angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  33. 33.In triangle ABC, angle A = 41° and angle B = 89°. What is angle C (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 53° and 54°. What is the exterior angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  37. 37.In triangle ABC, angle A = 34° and angle B = 85°. What is angle C (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 36° and 65°. What is the exterior angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?

Answer key

  1. 96
  2. 50
  3. 79
  4. 72
  5. Yes
  6. 57
  7. 72
  8. 8
  9. 90
  10. 110
  11. 15
  12. 76
  13. 72
  14. 30
  15. Yes
  16. 72
  17. 20
  18. 35
  19. 15
  20. 18
  21. Yes
  22. 39
  23. 40
  24. No
  25. 10
  26. 16
  27. 20
  28. 68
  29. 14
  30. 66
  31. 18
  32. 78
  33. 50
  34. 68
  35. 107
  36. 84
  37. 61
  38. 101
  39. 11
  40. 48

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