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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 364 · 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 = 73° and angle B = 24°. 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.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 65° and 32°. What is the exterior angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 72° and 79°. What is the exterior angle (in degrees)?
  7. 7.In triangle ABC, angle A = 75° and angle B = 40°. What is angle C (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 64°. What is each of the other two angles (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  10. 10.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 81° and angle B = 26°. What is angle C (in degrees)?
  12. 12.Can a triangle have sides of 4 cm, 4 cm and 2 cm? (a) Yes (b) No
  13. 13.In triangle ABC, angle A = 62° and angle B = 43°. What is angle C (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 54° and 23°. What is the exterior angle (in degrees)?
  16. 16.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  17. 17.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 84° and angle B = 66°. What is angle C (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  24. 24.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)?
  25. 25.The two interior opposite angles of a triangle are 25° and 25°. What is the exterior angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  27. 27.Can a triangle have sides of 8 cm, 8 cm and 19 cm? (a) Yes (b) No
  28. 28.Can a triangle have sides of 5 cm, 5 cm and 3 cm? (a) No (b) Yes
  29. 29.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  31. 31.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  32. 32.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  33. 33.In triangle ABC, angle A = 65° and angle B = 70°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 74° and angle B = 64°. What is angle C (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 76° and angle B = 78°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  38. 38.In triangle ABC, angle A = 90° and angle B = 44°. What is angle C (in degrees)?
  39. 39.An exterior angle of a triangle is 151°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  40. 40.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?

Answer key

  1. 83
  2. 90
  3. 72
  4. 97
  5. 72
  6. 151
  7. 65
  8. 58
  9. 25
  10. 134
  11. 73
  12. Yes
  13. 75
  14. 22
  15. 77
  16. 8
  17. 20
  18. 55
  19. 65
  20. 79
  21. 34
  22. 30
  23. 76
  24. 7
  25. 50
  26. 90
  27. No
  28. Yes
  29. 45
  30. 38
  31. 17
  32. 100
  33. 45
  34. 42
  35. 57
  36. 26
  37. 74
  38. 46
  39. 72
  40. 90

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