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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 611 · 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 angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 61° each. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 72° and angle B = 58°. What is angle C (in degrees)?
  5. 5.Can a triangle have sides of 9 cm, 9 cm and 3 cm? (a) Yes (b) No
  6. 6.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  8. 8.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 31° and 41°. What is the exterior angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 20° and 29°. What is the exterior angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  13. 13.Can a triangle have sides of 23 cm, 12 cm and 6 cm? (a) Yes (b) No
  14. 14.In triangle ABC, angle A = 86° and angle B = 21°. What is angle C (in degrees)?
  15. 15.Can a triangle have sides of 2 cm, 10 cm and 5 cm? (a) No (b) Yes
  16. 16.In triangle ABC, angle A = 31° and angle B = 101°. What is angle C (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  19. 19.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 92° and angle B = 37°. What is angle C (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 64° and 48°. What is the exterior angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 79° and angle B = 39°. What is angle C (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 64°. What is each of the other two angles (in degrees)?
  31. 31.In triangle ABC, angle A = 45° and angle B = 103°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 52° and angle B = 50°. What is angle C (in degrees)?
  33. 33.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 22° and 70°. What is the exterior angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  37. 37.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  38. 38.An exterior angle of a triangle is 123°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?

Answer key

  1. 18
  2. 54
  3. 58
  4. 50
  5. Yes
  6. 56
  7. 80
  8. 46
  9. 72
  10. 50
  11. 49
  12. 20
  13. No
  14. 73
  15. No
  16. 48
  17. 120
  18. 22
  19. 20
  20. 94
  21. 16
  22. 126
  23. 45
  24. 30
  25. 90
  26. 51
  27. 112
  28. 69
  29. 62
  30. 58
  31. 32
  32. 78
  33. 34
  34. 92
  35. 64
  36. 20
  37. 75
  38. 68
  39. 118
  40. 70

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