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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 292 · 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 60° each. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 27° and angle B = 57°. What is angle C (in degrees)?
  4. 4.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  5. 5.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  8. 8.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  9. 9.In triangle ABC, angle A = 38° and angle B = 23°. What is angle C (in degrees)?
  10. 10.In triangle ABC, angle A = 22° and angle B = 61°. What is angle C (in degrees)?
  11. 11.Can a triangle have sides of 9 cm, 17 cm and 6 cm? (a) Yes (b) No
  12. 12.In triangle ABC, angle A = 27° and angle B = 85°. What is angle C (in degrees)?
  13. 13.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)?
  14. 14.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  15. 15.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  16. 16.In triangle ABC, angle A = 74° and angle B = 40°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 70° and angle B = 73°. What is angle C (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 33° and angle B = 50°. What is angle C (in degrees)?
  20. 20.In triangle ABC, angle A = 28° and angle B = 94°. What is angle C (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 6 cm, 8 cm and 16 cm? (a) No (b) Yes
  23. 23.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  31. 31.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  32. 32.In triangle ABC, angle A = 50° and angle B = 44°. What is angle C (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 39° and 21°. What is the exterior angle (in degrees)?
  34. 34.In triangle ABC, angle A = 92° and angle B = 51°. What is angle C (in degrees)?
  35. 35.In triangle ABC, angle A = 78° and angle B = 70°. What is angle C (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  37. 37.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  39. 39.Can a triangle have sides of 3 cm, 16 cm and 10 cm? (a) Yes (b) No
  40. 40.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?

Answer key

  1. 60
  2. 64
  3. 96
  4. 51
  5. 76
  6. 16
  7. 30
  8. 80
  9. 119
  10. 97
  11. No
  12. 68
  13. 12
  14. 65
  15. 3
  16. 66
  17. 37
  18. 75
  19. 97
  20. 58
  21. 70
  22. No
  23. 37
  24. 108
  25. 44
  26. 71
  27. 32
  28. 102
  29. 45
  30. 72
  31. 15
  32. 86
  33. 60
  34. 37
  35. 32
  36. 17
  37. 90
  38. 36
  39. No
  40. 140

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