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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 78 · 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 = 74° and angle B = 76°. What is angle C (in degrees)?
  2. 2.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)?
  3. 3.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  4. 4.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  5. 5.Can a triangle have sides of 14 cm, 8 cm and 7 cm? (a) Yes (b) No
  6. 6.The two interior opposite angles of a triangle are 64° and 38°. What is the exterior angle (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  8. 8.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  9. 9.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  15. 15.In triangle ABC, angle A = 75° and angle B = 27°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 63° and angle B = 38°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 49° and angle B = 70°. What is angle C (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  20. 20.In triangle ABC, angle A = 75° and angle B = 29°. What is angle C (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 34° and 29°. What is the exterior angle (in degrees)?
  23. 23.Can a triangle have sides of 10 cm, 17 cm and 3 cm? (a) No (b) Yes
  24. 24.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  25. 25.In triangle ABC, angle A = 82° and angle B = 66°. What is angle C (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 53° and 24°. What is the exterior angle (in degrees)?
  27. 27.In triangle ABC, angle A = 33° and angle B = 56°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 3 cm, 16 cm and 8 cm? (a) No (b) Yes
  29. 29.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  30. 30.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 25° and 26°. What is the exterior angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  33. 33.In triangle ABC, angle A = 34° and angle B = 35°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 49° and angle B = 83°. What is angle C (in degrees)?
  35. 35.Can a triangle have sides of 4 cm, 7 cm and 10 cm? (a) No (b) Yes
  36. 36.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  37. 37.Can a triangle have sides of 6 cm, 8 cm and 12 cm? (a) Yes (b) No
  38. 38.The two interior opposite angles of a triangle are 54° and 24°. What is the exterior angle (in degrees)?
  39. 39.In triangle ABC, angle A = 27° and angle B = 78°. What is angle C (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?

Answer key

  1. 30
  2. 5
  3. 54
  4. 52
  5. Yes
  6. 102
  7. 12
  8. 4
  9. 138
  10. 126
  11. 90
  12. 60
  13. 76
  14. 40
  15. 78
  16. 79
  17. 70
  18. 61
  19. 25
  20. 76
  21. 31
  22. 63
  23. No
  24. 45
  25. 32
  26. 77
  27. 91
  28. No
  29. 44
  30. 47
  31. 51
  32. 90
  33. 111
  34. 48
  35. Yes
  36. 90
  37. Yes
  38. 78
  39. 75
  40. 46

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