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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 692 · 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 44° and 50°. What is the exterior angle (in degrees)?
  2. 2.In triangle ABC, angle A = 38° and angle B = 20°. What is angle C (in degrees)?
  3. 3.Can a triangle have sides of 11 cm, 7 cm and 8 cm? (a) Yes (b) No
  4. 4.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  6. 6.An exterior angle of a triangle is 123°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 76° and angle B = 48°. What is angle C (in degrees)?
  10. 10.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 69° and 64°. What is the exterior angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 86°. What is each of the other two angles (in degrees)?
  15. 15.In triangle ABC, angle A = 84° and angle B = 64°. What is angle C (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  17. 17.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  19. 19.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  20. 20.In triangle ABC, angle A = 85° and angle B = 58°. What is angle C (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  22. 22.In triangle ABC, angle A = 90° and angle B = 66°. What is angle C (in degrees)?
  23. 23.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  24. 24.In triangle ABC, angle A = 92° and angle B = 45°. What is angle C (in degrees)?
  25. 25.Can a triangle have sides of 8 cm, 1 cm and 8 cm? (a) Yes (b) No
  26. 26.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  27. 27.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  30. 30.Can a triangle have sides of 6 cm, 3 cm and 4 cm? (a) Yes (b) No
  31. 31.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  32. 32.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  34. 34.In triangle ABC, angle A = 44° and angle B = 22°. What is angle C (in degrees)?
  35. 35.Can a triangle have sides of 11 cm, 26 cm and 10 cm? (a) Yes (b) No
  36. 36.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  37. 37.Can a triangle have sides of 7 cm, 11 cm and 19 cm? (a) Yes (b) No
  38. 38.In triangle ABC, angle A = 76° and angle B = 77°. What is angle C (in degrees)?
  39. 39.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  40. 40.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?

Answer key

  1. 94
  2. 122
  3. Yes
  4. 5
  5. 30
  6. 57
  7. 65
  8. 48
  9. 56
  10. 45
  11. 133
  12. 67
  13. 23
  14. 47
  15. 32
  16. 84
  17. 53
  18. 50
  19. 44
  20. 37
  21. 39
  22. 24
  23. 15
  24. 43
  25. Yes
  26. 5
  27. 80
  28. 75
  29. 46
  30. Yes
  31. 25
  32. 37
  33. 26
  34. 114
  35. No
  36. 73
  37. No
  38. 27
  39. 6
  40. 36

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