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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 683 · 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 25 cm, 9 cm and 12 cm? (a) Yes (b) No
  2. 2.The two interior opposite angles of a triangle are 28° and 70°. What is the exterior angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  4. 4.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  6. 6.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  7. 7.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  8. 8.Can a triangle have sides of 10 cm, 24 cm and 10 cm? (a) Yes (b) No
  9. 9.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  10. 10.An exterior angle of a triangle is 138°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  11. 11.An exterior angle of a triangle is 62°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  13. 13.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  14. 14.In triangle ABC, angle A = 45° and angle B = 58°. What is angle C (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  16. 16.In triangle ABC, angle A = 33° and angle B = 96°. What is angle C (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  19. 19.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  20. 20.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  21. 21.In triangle ABC, angle A = 46° and angle B = 79°. What is angle C (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 124°. What is each of the other two angles (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  24. 24.In triangle ABC, angle A = 66° and angle B = 86°. What is angle C (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 83° and angle B = 21°. What is angle C (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  29. 29.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  31. 31.In triangle ABC, angle A = 72° and angle B = 64°. What is angle C (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  33. 33.In triangle ABC, angle A = 93° and angle B = 48°. What is angle C (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 50° and angle B = 67°. What is angle C (in degrees)?
  36. 36.An exterior angle of a triangle is 69°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  37. 37.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  38. 38.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)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  40. 40.In triangle ABC, angle A = 34° and angle B = 86°. What is angle C (in degrees)?

Answer key

  1. No
  2. 98
  3. 30
  4. 34
  5. 17
  6. 46
  7. 48
  8. No
  9. 10
  10. 72
  11. 41
  12. 76
  13. 58
  14. 77
  15. 62
  16. 51
  17. 16
  18. 10
  19. 36
  20. 100
  21. 55
  22. 28
  23. 72
  24. 28
  25. 49
  26. 76
  27. 59
  28. 25
  29. 72
  30. 46
  31. 44
  32. 118
  33. 39
  34. 44
  35. 63
  36. 31
  37. 10
  38. 6
  39. 74
  40. 60

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