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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 868 · 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 = 86° and angle B = 21°. What is angle C (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 4 cm, 11 cm and 11 cm? (a) Yes (b) No
  5. 5.In triangle ABC, angle A = 80° and angle B = 21°. What is angle C (in degrees)?
  6. 6.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  8. 8.In triangle ABC, angle A = 45° and angle B = 104°. What is angle C (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  10. 10.Can a triangle have sides of 9 cm, 14 cm and 5 cm? (a) Yes (b) No
  11. 11.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  12. 12.An exterior angle of a triangle is 125°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  15. 15.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  18. 18.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  19. 19.In triangle ABC, angle A = 23° and angle B = 56°. What is angle C (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  22. 22.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 94°. What is each of the other two angles (in degrees)?
  25. 25.In triangle ABC, angle A = 74° and angle B = 70°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 30° and angle B = 109°. What is angle C (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  30. 30.The two interior opposite angles of a triangle are 40° and 35°. What is the exterior angle (in degrees)?
  31. 31.An exterior angle of a triangle is 44°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  32. 32.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  34. 34.Can a triangle have sides of 13 cm, 2 cm and 10 cm? (a) No (b) Yes
  35. 35.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  38. 38.In triangle ABC, angle A = 93° and angle B = 31°. What is angle C (in degrees)?
  39. 39.In triangle ABC, angle A = 66° and angle B = 74°. What is angle C (in degrees)?
  40. 40.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?

Answer key

  1. 73
  2. 40
  3. 124
  4. Yes
  5. 79
  6. 70
  7. 39
  8. 31
  9. 100
  10. No
  11. 20
  12. 50
  13. 55
  14. 42
  15. 30
  16. 20
  17. 60
  18. 64
  19. 101
  20. 18
  21. 73
  22. 30
  23. 74
  24. 43
  25. 36
  26. 49
  27. 41
  28. 75
  29. 5
  30. 75
  31. 23
  32. 58
  33. 72
  34. No
  35. 60
  36. 56
  37. 12
  38. 56
  39. 40
  40. 34

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