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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 103 · 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.The two interior opposite angles of a triangle are 40° and 73°. What is the exterior angle (in degrees)?
  2. 2.Can a triangle have sides of 9 cm, 7 cm and 9 cm? (a) No (b) Yes
  3. 3.In triangle ABC, angle A = 20° and angle B = 88°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 31° and angle B = 111°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 86° and angle B = 72°. What is angle C (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 42° and angle B = 116°. What is angle C (in degrees)?
  11. 11.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 37°. What is the other one (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 two interior opposite angles of a triangle are 57° and 47°. What is the exterior angle (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  15. 15.In triangle ABC, angle A = 34° and angle B = 107°. What is angle C (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  17. 17.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  18. 18.Can a triangle have sides of 4 cm, 4 cm and 1 cm? (a) Yes (b) No
  19. 19.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  20. 20.An exterior angle of a triangle is 147°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  21. 21.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  22. 22.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  23. 23.In triangle ABC, angle A = 92° and angle B = 23°. What is angle C (in degrees)?
  24. 24.In triangle ABC, angle A = 31° and angle B = 97°. What is angle C (in degrees)?
  25. 25.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  26. 26.In triangle ABC, angle A = 31° and angle B = 72°. What is angle C (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  28. 28.Can a triangle have sides of 8 cm, 2 cm and 9 cm? (a) Yes (b) No
  29. 29.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)?
  30. 30.Can a triangle have sides of 2 cm, 4 cm and 7 cm? (a) No (b) Yes
  31. 31.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  33. 33.In triangle ABC, angle A = 91° and angle B = 25°. What is angle C (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 54° each. What is the third angle (in degrees)?
  36. 36.Can a triangle have sides of 4 cm, 10 cm and 10 cm? (a) No (b) Yes
  37. 37.Can a triangle have sides of 12 cm, 12 cm and 4 cm? (a) No (b) Yes
  38. 38.In triangle ABC, angle A = 51° and angle B = 76°. What is angle C (in degrees)?
  39. 39.In triangle ABC, angle A = 45° and angle B = 22°. What is angle C (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?

Answer key

  1. 113
  2. Yes
  3. 72
  4. 36
  5. 20
  6. 24
  7. 38
  8. 22
  9. 73
  10. 22
  11. 47
  12. 49
  13. 104
  14. 25
  15. 39
  16. 25
  17. 66
  18. Yes
  19. 38
  20. 71
  21. 8
  22. 75
  23. 65
  24. 52
  25. 20
  26. 77
  27. 13
  28. Yes
  29. 24
  30. No
  31. 20
  32. 16
  33. 64
  34. 62
  35. 72
  36. Yes
  37. Yes
  38. 53
  39. 113
  40. 114

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