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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 439 · 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 3 cm, 15 cm and 12 cm? (a) Yes (b) No
  2. 2.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  5. 5.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  6. 6.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  7. 7.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 36° and 48°. What is the exterior angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  14. 14.In triangle ABC, angle A = 33° and angle B = 121°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 20° and angle B = 20°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 72° and angle B = 52°. What is angle C (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  20. 20.In triangle ABC, angle A = 80° and angle B = 57°. 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.Can a triangle have sides of 25 cm, 12 cm and 9 cm? (a) No (b) Yes
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  26. 26.In triangle ABC, angle A = 84° and angle B = 66°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 2 cm, 2 cm and 3 cm? (a) Yes (b) No
  28. 28.In triangle ABC, angle A = 92° and angle B = 50°. What is angle C (in degrees)?
  29. 29.Can a triangle have sides of 12 cm, 19 cm and 9 cm? (a) Yes (b) No
  30. 30.Can a triangle have sides of 12 cm, 14 cm and 7 cm? (a) Yes (b) No
  31. 31.In triangle ABC, angle A = 34° and angle B = 54°. What is angle C (in degrees)?
  32. 32.Can a triangle have sides of 18 cm, 5 cm and 12 cm? (a) No (b) Yes
  33. 33.Can a triangle have sides of 7 cm, 7 cm and 14 cm? (a) No (b) Yes
  34. 34.In triangle ABC, angle A = 98° and angle B = 54°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  36. 36.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?

Answer key

  1. No
  2. 76
  3. 71
  4. 80
  5. 61
  6. 17
  7. 70
  8. 84
  9. 90
  10. 64
  11. 90
  12. 54
  13. 15
  14. 26
  15. 140
  16. 56
  17. 36
  18. 108
  19. 84
  20. 43
  21. 54
  22. No
  23. 120
  24. 53
  25. 27
  26. 30
  27. Yes
  28. 38
  29. Yes
  30. Yes
  31. 92
  32. No
  33. No
  34. 28
  35. 72
  36. 47
  37. 23
  38. 12
  39. 100
  40. 20

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