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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 139 · 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.Can a triangle have sides of 4 cm, 8 cm and 13 cm? (a) Yes (b) No
  2. 2.Can a triangle have sides of 13 cm, 4 cm and 10 cm? (a) Yes (b) No
  3. 3.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 46° and angle B = 83°. What is angle C (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  6. 6.In triangle ABC, angle A = 41° and angle B = 35°. What is angle C (in degrees)?
  7. 7.Can a triangle have sides of 12 cm, 22 cm and 9 cm? (a) No (b) Yes
  8. 8.In triangle ABC, angle A = 46° and angle B = 102°. What is angle C (in degrees)?
  9. 9.In triangle ABC, angle A = 53° and angle B = 72°. What is angle C (in degrees)?
  10. 10.In triangle ABC, angle A = 97° and angle B = 21°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 89° and angle B = 64°. What is angle C (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 50° and 48°. What is the exterior angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  15. 15.Can a triangle have sides of 2 cm, 4 cm and 8 cm? (a) Yes (b) No
  16. 16.The two interior opposite angles of a triangle are 61° and 65°. What is the exterior angle (in degrees)?
  17. 17.In triangle ABC, angle A = 56° and angle B = 65°. What is angle C (in degrees)?
  18. 18.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  21. 21.Can a triangle have sides of 8 cm, 4 cm and 5 cm? (a) No (b) Yes
  22. 22.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 60° and 27°. What is the exterior angle (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 23 cm, 11 cm and 7 cm? (a) Yes (b) No
  26. 26.In triangle ABC, angle A = 92° and angle B = 67°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 34° and angle B = 48°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 9 cm, 6 cm and 11 cm? (a) Yes (b) No
  29. 29.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  31. 31.Can a triangle have sides of 9 cm, 9 cm and 2 cm? (a) Yes (b) No
  32. 32.In triangle ABC, angle A = 33° and angle B = 28°. What is angle C (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  35. 35.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  36. 36.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  38. 38.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)?
  39. 39.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  40. 40.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?

Answer key

  1. No
  2. Yes
  3. 13
  4. 51
  5. 13
  6. 104
  7. No
  8. 32
  9. 55
  10. 62
  11. 27
  12. 70
  13. 98
  14. 48
  15. No
  16. 126
  17. 59
  18. 75
  19. 41
  20. 40
  21. Yes
  22. 72
  23. 87
  24. 114
  25. No
  26. 21
  27. 98
  28. Yes
  29. 31
  30. 36
  31. Yes
  32. 119
  33. 22
  34. 14
  35. 6
  36. 23
  37. 50
  38. 15
  39. 90
  40. 70

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