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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 172 · 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 22°. What is the third angle (in degrees)?
  2. 2.Can a triangle have sides of 17 cm, 2 cm and 10 cm? (a) No (b) Yes
  3. 3.In triangle ABC, angle A = 38° and angle B = 65°. What is angle C (in degrees)?
  4. 4.In triangle ABC, angle A = 59° and angle B = 49°. What is angle C (in degrees)?
  5. 5.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  6. 6.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  7. 7.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 12 cm, 10 cm and 20 cm? (a) Yes (b) No
  11. 11.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  12. 12.In triangle ABC, angle A = 28° and angle B = 97°. What is angle C (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  15. 15.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  16. 16.In triangle ABC, angle A = 83° and angle B = 65°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  21. 21.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  23. 23.An exterior angle of a triangle is 50°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  25. 25.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 33° and angle B = 85°. What is angle C (in degrees)?
  27. 27.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  28. 28.Can a triangle have sides of 5 cm, 8 cm and 6 cm? (a) No (b) Yes
  29. 29.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  30. 30.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  31. 31.In triangle ABC, angle A = 53° and angle B = 33°. What is angle C (in degrees)?
  32. 32.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  34. 34.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 67° and 43°. What is the exterior angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  39. 39.In triangle ABC, angle A = 67° and angle B = 49°. What is angle C (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?

Answer key

  1. 68
  2. No
  3. 77
  4. 72
  5. 7
  6. 10
  7. 15
  8. 98
  9. 25
  10. Yes
  11. 67
  12. 55
  13. 20
  14. 49
  15. 48
  16. 32
  17. 77
  18. 60
  19. 31
  20. 42
  21. 73
  22. 66
  23. 28
  24. 22
  25. 72
  26. 62
  27. 75
  28. Yes
  29. 75
  30. 27
  31. 94
  32. 40
  33. 71
  34. 45
  35. 110
  36. 46
  37. 126
  38. 124
  39. 64
  40. 38

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