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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 662 · 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.

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  1. 1.The two interior opposite angles of a triangle are 33° and 30°. What is the exterior angle (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 54° each. What is the third angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  4. 4.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)?
  5. 5.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  6. 6.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 27° and 24°. What is the exterior angle (in degrees)?
  8. 8.Can a triangle have sides of 11 cm, 4 cm and 4 cm? (a) No (b) Yes
  9. 9.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 73° and angle B = 45°. What is angle C (in degrees)?
  12. 12.In triangle ABC, angle A = 72° and angle B = 48°. What is angle C (in degrees)?
  13. 13.In triangle ABC, angle A = 97° and angle B = 59°. What is angle C (in degrees)?
  14. 14.In triangle ABC, angle A = 61° and angle B = 50°. What is angle C (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  18. 18.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  19. 19.In triangle ABC, angle A = 90° and angle B = 29°. What is angle C (in degrees)?
  20. 20.In triangle ABC, angle A = 72° and angle B = 43°. What is angle C (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  23. 23.Can a triangle have sides of 3 cm, 2 cm and 4 cm? (a) Yes (b) No
  24. 24.Can a triangle have sides of 10 cm, 8 cm and 12 cm? (a) Yes (b) No
  25. 25.In triangle ABC, angle A = 66° and angle B = 91°. What is angle C (in degrees)?
  26. 26.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)?
  27. 27.In triangle ABC, angle A = 21° and angle B = 108°. What is angle C (in degrees)?
  28. 28.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  29. 29.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  30. 30.Can a triangle have sides of 10 cm, 11 cm and 23 cm? (a) No (b) Yes
  31. 31.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  35. 35.In triangle ABC, angle A = 66° and angle B = 61°. What is angle C (in degrees)?
  36. 36.Can a triangle have sides of 8 cm, 15 cm and 8 cm? (a) No (b) Yes
  37. 37.In triangle ABC, angle A = 43° and angle B = 92°. What is angle C (in degrees)?
  38. 38.In triangle ABC, angle A = 83° and angle B = 71°. What is angle C (in degrees)?
  39. 39.Can a triangle have sides of 5 cm, 6 cm and 13 cm? (a) Yes (b) No
  40. 40.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?

Answer key

  1. 63
  2. 72
  3. 48
  4. 7
  5. 5
  6. 38
  7. 51
  8. No
  9. 36
  10. 10
  11. 62
  12. 60
  13. 24
  14. 69
  15. 12
  16. 77
  17. 68
  18. 5
  19. 61
  20. 65
  21. 64
  22. 19
  23. Yes
  24. Yes
  25. 23
  26. 12
  27. 51
  28. 20
  29. 67
  30. No
  31. 30
  32. 61
  33. 130
  34. 39
  35. 53
  36. Yes
  37. 45
  38. 26
  39. No
  40. 43

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