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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 664 · 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.

NameDateTime takenScore ___ / 40
  1. 1.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  2. 2.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  3. 3.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 71° and angle B = 44°. What is angle C (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  8. 8.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  10. 10.In triangle ABC, angle A = 60° and angle B = 89°. What is angle C (in degrees)?
  11. 11.Can a triangle have sides of 11 cm, 12 cm and 3 cm? (a) Yes (b) No
  12. 12.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  13. 13.The two interior opposite angles of a triangle are 36° and 27°. What is the exterior angle (in degrees)?
  14. 14.Can a triangle have sides of 8 cm, 9 cm and 11 cm? (a) No (b) Yes
  15. 15.Can a triangle have sides of 4 cm, 3 cm and 2 cm? (a) No (b) Yes
  16. 16.The two interior opposite angles of a triangle are 46° and 45°. What is the exterior angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 70° each. What is the third 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.In triangle ABC, angle A = 66° and angle B = 43°. What is angle C (in degrees)?
  21. 21.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 3 cm, 7 cm and 7 cm? (a) No (b) Yes
  25. 25.In triangle ABC, angle A = 82° and angle B = 27°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 9 cm, 20 cm and 11 cm? (a) No (b) Yes
  30. 30.Can a triangle have sides of 25 cm, 10 cm and 10 cm? (a) Yes (b) No
  31. 31.Can a triangle have sides of 2 cm, 8 cm and 4 cm? (a) No (b) Yes
  32. 32.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  36. 36.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  37. 37.The two interior opposite angles of a triangle are 36° and 26°. What is the exterior angle (in degrees)?
  38. 38.In triangle ABC, angle A = 40° and angle B = 113°. What is angle C (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?

Answer key

  1. 34
  2. 72
  3. 39
  4. 20
  5. 64
  6. 65
  7. 17
  8. 15
  9. 20
  10. 31
  11. Yes
  12. 12
  13. 63
  14. Yes
  15. Yes
  16. 91
  17. 39
  18. 40
  19. 70
  20. 71
  21. 40
  22. 75
  23. 116
  24. Yes
  25. 71
  26. 76
  27. 44
  28. 134
  29. No
  30. No
  31. No
  32. 28
  33. 62
  34. 124
  35. 100
  36. 8
  37. 62
  38. 27
  39. 31
  40. 22

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