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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 182 · 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 an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  2. 2.In triangle ABC, angle A = 75° and angle B = 31°. What is angle C (in degrees)?
  3. 3.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  5. 5.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  6. 6.The two interior opposite angles of a triangle are 37° and 47°. What is the exterior angle (in degrees)?
  7. 7.Can a triangle have sides of 20 cm, 10 cm and 10 cm? (a) Yes (b) No
  8. 8.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 33° and 49°. What is the exterior angle (in degrees)?
  10. 10.In triangle ABC, angle A = 80° and angle B = 44°. What is angle C (in degrees)?
  11. 11.Can a triangle have sides of 2 cm, 6 cm and 8 cm? (a) No (b) Yes
  12. 12.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  15. 15.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 76°. What is each of the other two angles (in degrees)?
  18. 18.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  21. 21.In triangle ABC, angle A = 29° and angle B = 120°. What is angle C (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 10 cm, 15 cm and 10 cm? (a) No (b) Yes
  25. 25.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 47° and angle B = 89°. What is angle C (in degrees)?
  28. 28.In triangle ABC, angle A = 81° and angle B = 50°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 85° and angle B = 49°. What is angle C (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 70° and 35°. What is the exterior angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 9 cm, 5 cm and 10 cm? (a) Yes (b) No
  35. 35.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  37. 37.In triangle ABC, angle A = 42° and angle B = 100°. What is angle C (in degrees)?
  38. 38.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  39. 39.In triangle ABC, angle A = 22° and angle B = 71°. What is angle C (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 33° and 52°. What is the exterior angle (in degrees)?

Answer key

  1. 74
  2. 74
  3. 76
  4. 138
  5. 12
  6. 84
  7. No
  8. 72
  9. 82
  10. 56
  11. No
  12. 25
  13. 44
  14. 39
  15. 72
  16. 55
  17. 52
  18. 59
  19. 25
  20. 66
  21. 31
  22. 132
  23. 30
  24. Yes
  25. 12
  26. 61
  27. 44
  28. 49
  29. 46
  30. 105
  31. 77
  32. 88
  33. 12
  34. Yes
  35. 58
  36. 31
  37. 38
  38. 20
  39. 87
  40. 85

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