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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 288 · 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.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  2. 2.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  3. 3.Can a triangle have sides of 8 cm, 11 cm and 3 cm? (a) No (b) Yes
  4. 4.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 75° and angle B = 26°. What is angle C (in degrees)?
  8. 8.Can a triangle have sides of 12 cm, 4 cm and 17 cm? (a) Yes (b) No
  9. 9.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  11. 11.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  12. 12.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 62° and angle B = 45°. What is angle C (in degrees)?
  14. 14.Can a triangle have sides of 12 cm, 5 cm and 7 cm? (a) Yes (b) No
  15. 15.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  16. 16.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  17. 17.In triangle ABC, angle A = 96° and angle B = 42°. What is angle C (in degrees)?
  18. 18.Can a triangle have sides of 2 cm, 9 cm and 3 cm? (a) No (b) Yes
  19. 19.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  20. 20.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 47° and 62°. What is the exterior angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  23. 23.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)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  25. 25.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  26. 26.In triangle ABC, angle A = 85° and angle B = 36°. What is angle C (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  29. 29.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  30. 30.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 4 cm, 9 cm and 6 cm? (a) Yes (b) No
  32. 32.In triangle ABC, angle A = 27° and angle B = 117°. What is angle C (in degrees)?
  33. 33.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  35. 35.In triangle ABC, angle A = 28° and angle B = 65°. What is angle C (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles (in degrees)?
  37. 37.In triangle ABC, angle A = 35° and angle B = 89°. What is angle C (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 30° and 74°. What is the exterior angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?

Answer key

  1. 45
  2. 38
  3. No
  4. 130
  5. 20
  6. 31
  7. 79
  8. No
  9. 30
  10. 25
  11. 36
  12. 52
  13. 73
  14. No
  15. 70
  16. 51
  17. 42
  18. No
  19. 37
  20. 68
  21. 109
  22. 100
  23. 15
  24. 27
  25. 37
  26. 59
  27. 54
  28. 51
  29. 12
  30. 77
  31. Yes
  32. 36
  33. 75
  34. 90
  35. 87
  36. 40
  37. 56
  38. 104
  39. 18
  40. 72

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