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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 913 · 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.In triangle ABC, angle A = 68° and angle B = 69°. What is angle C (in degrees)?
  2. 2.Can a triangle have sides of 11 cm, 10 cm and 18 cm? (a) Yes (b) No
  3. 3.Can a triangle have sides of 11 cm, 13 cm and 8 cm? (a) No (b) Yes
  4. 4.Can a triangle have sides of 2 cm, 11 cm and 11 cm? (a) Yes (b) No
  5. 5.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  6. 6.In triangle ABC, angle A = 80° and angle B = 54°. What is angle C (in degrees)?
  7. 7.Can a triangle have sides of 9 cm, 3 cm and 8 cm? (a) No (b) Yes
  8. 8.In triangle ABC, angle A = 65° and angle B = 50°. What is angle C (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 25° and 69°. What is the exterior angle (in degrees)?
  12. 12.In triangle ABC, angle A = 54° and angle B = 28°. What is angle C (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  14. 14.Can a triangle have sides of 2 cm, 8 cm and 7 cm? (a) No (b) Yes
  15. 15.In triangle ABC, angle A = 55° and angle B = 28°. What is angle C (in degrees)?
  16. 16.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  19. 19.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  20. 20.In triangle ABC, angle A = 95° and angle B = 27°. What is angle C (in degrees)?
  21. 21.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 51° and angle B = 46°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 62° and angle B = 20°. What is angle C (in degrees)?
  26. 26.In triangle ABC, angle A = 31° and angle B = 23°. What is angle C (in degrees)?
  27. 27.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  28. 28.An exterior angle of a triangle is 136°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  29. 29.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  30. 30.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  32. 32.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  33. 33.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  34. 34.An exterior angle of a triangle is 155°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  35. 35.In triangle ABC, angle A = 94° and angle B = 57°. What is angle C (in degrees)?
  36. 36.Can a triangle have sides of 13 cm, 9 cm and 2 cm? (a) Yes (b) No
  37. 37.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  40. 40.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?

Answer key

  1. 43
  2. Yes
  3. Yes
  4. Yes
  5. 17
  6. 46
  7. Yes
  8. 65
  9. 126
  10. 36
  11. 94
  12. 98
  13. 67
  14. Yes
  15. 97
  16. 42
  17. 25
  18. 34
  19. 34
  20. 58
  21. 54
  22. 63
  23. 21
  24. 83
  25. 98
  26. 126
  27. 24
  28. 60
  29. 20
  30. 41
  31. 64
  32. 76
  33. 67
  34. 77
  35. 29
  36. No
  37. 80
  38. 48
  39. 45
  40. 72

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