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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 539 · 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 25° and 49°. What is the exterior angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 55° and 39°. What is the exterior angle (in degrees)?
  5. 5.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  6. 6.An exterior angle of a triangle is 42°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  7. 7.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  8. 8.In triangle ABC, angle A = 64° and angle B = 62°. What is angle C (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 45° and 48°. What is the exterior angle (in degrees)?
  14. 14.In triangle ABC, angle A = 85° and angle B = 62°. What is angle C (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 78° and angle B = 76°. What is angle C (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 76° and 75°. What is the exterior angle (in degrees)?
  19. 19.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  20. 20.In triangle ABC, angle A = 91° and angle B = 55°. What is angle C (in degrees)?
  21. 21.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  22. 22.In triangle ABC, angle A = 55° and angle B = 60°. What is angle C (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 10 cm, 22 cm and 10 cm? (a) Yes (b) No
  26. 26.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  29. 29.The two interior opposite angles of a triangle are 60° and 34°. What is the exterior angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 45° and angle B = 68°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 74° and angle B = 27°. What is angle C (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  35. 35.In triangle ABC, angle A = 68° and angle B = 36°. What is angle C (in degrees)?
  36. 36.Can a triangle have sides of 3 cm, 3 cm and 7 cm? (a) Yes (b) No
  37. 37.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  38. 38.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  39. 39.In triangle ABC, angle A = 72° and angle B = 36°. What is angle C (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 55° and 48°. What is the exterior angle (in degrees)?

Answer key

  1. 74
  2. 45
  3. 30
  4. 94
  5. 35
  6. 20
  7. 18
  8. 54
  9. 52
  10. 77
  11. 63
  12. 134
  13. 93
  14. 33
  15. 77
  16. 60
  17. 26
  18. 151
  19. 37
  20. 34
  21. 40
  22. 65
  23. 62
  24. 17
  25. No
  26. 28
  27. 64
  28. 30
  29. 94
  30. 24
  31. 67
  32. 79
  33. 42
  34. 53
  35. 76
  36. No
  37. 20
  38. 39
  39. 72
  40. 103

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