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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 96 · 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.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  3. 3.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  4. 4.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 56° and 54°. What is the exterior angle (in degrees)?
  6. 6.Can a triangle have sides of 10 cm, 18 cm and 5 cm? (a) No (b) Yes
  7. 7.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  8. 8.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 32° and 44°. What is the exterior angle (in degrees)?
  10. 10.In triangle ABC, angle A = 48° and angle B = 68°. What is angle C (in degrees)?
  11. 11.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  12. 12.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  13. 13.Can a triangle have sides of 14 cm, 3 cm and 9 cm? (a) No (b) Yes
  14. 14.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  15. 15.Can a triangle have sides of 10 cm, 22 cm and 7 cm? (a) No (b) Yes
  16. 16.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)?
  17. 17.In triangle ABC, angle A = 38° and angle B = 101°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 37° and angle B = 122°. What is angle C (in degrees)?
  19. 19.Can a triangle have sides of 8 cm, 4 cm and 16 cm? (a) No (b) Yes
  20. 20.In triangle ABC, angle A = 54° and angle B = 47°. What is angle C (in degrees)?
  21. 21.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  22. 22.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  27. 27.Can a triangle have sides of 5 cm, 8 cm and 3 cm? (a) Yes (b) No
  28. 28.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  29. 29.Can a triangle have sides of 12 cm, 8 cm and 5 cm? (a) No (b) Yes
  30. 30.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  31. 31.In triangle ABC, angle A = 47° and angle B = 81°. What is angle C (in degrees)?
  32. 32.Can a triangle have sides of 16 cm, 7 cm and 11 cm? (a) No (b) Yes
  33. 33.Can a triangle have sides of 1 cm, 9 cm and 9 cm? (a) No (b) Yes
  34. 34.An exterior angle of a triangle is 51°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  35. 35.In triangle ABC, angle A = 23° and angle B = 84°. What is angle C (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?
  37. 37.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  38. 38.In triangle ABC, angle A = 23° and angle B = 91°. What is angle C (in degrees)?
  39. 39.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?

Answer key

  1. 65
  2. 20
  3. 37
  4. 75
  5. 110
  6. No
  7. 23
  8. 58
  9. 76
  10. 64
  11. 78
  12. 74
  13. No
  14. 13
  15. No
  16. 8
  17. 41
  18. 21
  19. No
  20. 79
  21. 70
  22. 42
  23. 90
  24. 88
  25. 79
  26. 64
  27. No
  28. 13
  29. Yes
  30. 36
  31. 52
  32. Yes
  33. Yes
  34. 30
  35. 73
  36. 79
  37. 60
  38. 66
  39. 72
  40. 72

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