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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 905 · 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.In triangle ABC, angle A = 28° and angle B = 95°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  3. 3.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  5. 5.In triangle ABC, angle A = 31° and angle B = 90°. What is angle C (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 33° and angle B = 34°. What is angle C (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 86°. What is each of the other two angles (in degrees)?
  11. 11.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  12. 12.In triangle ABC, angle A = 32° and angle B = 40°. What is angle C (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  18. 18.The two interior opposite angles of a triangle are 47° and 30°. What is the exterior angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 44° and 27°. What is the exterior angle (in degrees)?
  23. 23.Can a triangle have sides of 12 cm, 7 cm and 12 cm? (a) No (b) Yes
  24. 24.In an isosceles triangle, the two equal angles are 50° each. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 69° and angle B = 78°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 48° and angle B = 111°. What is angle C (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 24° and 32°. What is the exterior angle (in degrees)?
  29. 29.In triangle ABC, angle A = 72° and angle B = 52°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 58° and angle B = 71°. What is angle C (in degrees)?
  31. 31.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  32. 32.Can a triangle have sides of 13 cm, 4 cm and 6 cm? (a) No (b) Yes
  33. 33.Can a triangle have sides of 25 cm, 10 cm and 12 cm? (a) Yes (b) No
  34. 34.The two interior opposite angles of a triangle are 22° and 66°. What is the exterior angle (in degrees)?
  35. 35.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  36. 36.In triangle ABC, angle A = 21° and angle B = 118°. What is angle C (in degrees)?
  37. 37.In triangle ABC, angle A = 85° and angle B = 59°. What is angle C (in degrees)?
  38. 38.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  40. 40.Can a triangle have sides of 10 cm, 9 cm and 9 cm? (a) Yes (b) No

Answer key

  1. 57
  2. 90
  3. 80
  4. 10
  5. 59
  6. 60
  7. 113
  8. 41
  9. 50
  10. 47
  11. 62
  12. 108
  13. 25
  14. 19
  15. 75
  16. 19
  17. 17
  18. 77
  19. 70
  20. 72
  21. 47
  22. 71
  23. Yes
  24. 80
  25. 33
  26. 13
  27. 21
  28. 56
  29. 56
  30. 51
  31. 26
  32. No
  33. No
  34. 88
  35. 34
  36. 41
  37. 36
  38. 48
  39. 20
  40. Yes

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