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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 98 · 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 5 : 6 : 7. What is the biggest angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 80° and 64°. What is the exterior angle (in degrees)?
  3. 3.In triangle ABC, angle A = 83° and angle B = 26°. What is angle C (in degrees)?
  4. 4.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  5. 5.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)?
  6. 6.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 80° and angle B = 56°. What is angle C (in degrees)?
  10. 10.Can a triangle have sides of 11 cm, 5 cm and 5 cm? (a) Yes (b) No
  11. 11.In triangle ABC, angle A = 66° and angle B = 41°. What is angle C (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  13. 13.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  14. 14.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  15. 15.Can a triangle have sides of 8 cm, 7 cm and 14 cm? (a) Yes (b) No
  16. 16.Can a triangle have sides of 8 cm, 9 cm and 9 cm? (a) Yes (b) No
  17. 17.In triangle ABC, angle A = 75° and angle B = 73°. What is angle C (in degrees)?
  18. 18.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 72° and angle B = 79°. What is angle C (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  25. 25.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 57° and angle B = 62°. What is angle C (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 41° and 74°. What is the exterior angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 18°. 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 a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  36. 36.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  38. 38.An exterior angle of a triangle is 150°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  40. 40.In triangle ABC, angle A = 88° and angle B = 49°. What is angle C (in degrees)?

Answer key

  1. 70
  2. 144
  3. 71
  4. 15
  5. 7
  6. 41
  7. 72
  8. 46
  9. 44
  10. No
  11. 73
  12. 49
  13. 10
  14. 52
  15. Yes
  16. Yes
  17. 32
  18. 84
  19. 67
  20. 75
  21. 29
  22. 35
  23. 90
  24. 25
  25. 30
  26. 77
  27. 61
  28. 115
  29. 40
  30. 73
  31. 37
  32. 72
  33. 130
  34. 76
  35. 17
  36. 38
  37. 33
  38. 77
  39. 44
  40. 43

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