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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 147 · 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 longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  2. 2.In triangle ABC, angle A = 90° and angle B = 38°. What is angle C (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 63° and angle B = 25°. What is angle C (in degrees)?
  7. 7.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  8. 8.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  10. 10.In triangle ABC, angle A = 66° and angle B = 93°. What is angle C (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  15. 15.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  16. 16.In triangle ABC, angle A = 36° and angle B = 98°. What is angle C (in degrees)?
  17. 17.Can a triangle have sides of 11 cm, 10 cm and 4 cm? (a) No (b) Yes
  18. 18.Can a triangle have sides of 9 cm, 9 cm and 6 cm? (a) No (b) Yes
  19. 19.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  20. 20.In triangle ABC, angle A = 81° and angle B = 63°. What is angle C (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  22. 22.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 29° and 27°. What is the exterior angle (in degrees)?
  26. 26.In triangle ABC, angle A = 38° and angle B = 33°. What is angle C (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  30. 30.In triangle ABC, angle A = 30° and angle B = 84°. What is angle C (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 28° and 36°. What is the exterior angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  35. 35.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  36. 36.In triangle ABC, angle A = 39° and angle B = 105°. What is angle C (in degrees)?
  37. 37.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 59° and 20°. What is the exterior angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 43° and 60°. What is the exterior angle (in degrees)?
  40. 40.In triangle ABC, angle A = 97° and angle B = 42°. What is angle C (in degrees)?

Answer key

  1. 7
  2. 52
  3. 130
  4. 54
  5. 62
  6. 92
  7. 36
  8. 35
  9. 25
  10. 21
  11. 79
  12. 26
  13. 22
  14. 100
  15. 34
  16. 46
  17. Yes
  18. Yes
  19. 45
  20. 36
  21. 44
  22. 58
  23. 13
  24. 20
  25. 56
  26. 109
  27. 33
  28. 80
  29. 16
  30. 66
  31. 46
  32. 16
  33. 64
  34. 12
  35. 33
  36. 36
  37. 29
  38. 79
  39. 103
  40. 41

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