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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 416 · 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 angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 62° and angle B = 48°. What is angle C (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 28° and 36°. What is the exterior angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 25° and 28°. What is the exterior angle (in degrees)?
  9. 9.In triangle ABC, angle A = 82° and angle B = 42°. What is angle C (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  11. 11.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 30° and 48°. What is the exterior angle (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  14. 14.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  15. 15.An exterior angle of a triangle is 65°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  17. 17.In triangle ABC, angle A = 42° and angle B = 82°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 47° and angle B = 27°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  20. 20.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  21. 21.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  26. 26.Can a triangle have sides of 3 cm, 5 cm and 12 cm? (a) No (b) Yes
  27. 27.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  28. 28.The two interior opposite angles of a triangle are 49° and 40°. What is the exterior angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  31. 31.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  32. 32.Can a triangle have sides of 19 cm, 8 cm and 6 cm? (a) Yes (b) No
  33. 33.In triangle ABC, angle A = 68° and angle B = 24°. What is angle C (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  36. 36.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  37. 37.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 79° and angle B = 51°. What is angle C (in degrees)?
  39. 39.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 76° and 73°. What is the exterior angle (in degrees)?

Answer key

  1. 36
  2. 96
  3. 70
  4. 65
  5. 63
  6. 64
  7. 40
  8. 53
  9. 56
  10. 59
  11. 29
  12. 78
  13. 15
  14. 29
  15. 38
  16. 22
  17. 56
  18. 106
  19. 48
  20. 38
  21. 90
  22. 60
  23. 11
  24. 79
  25. 18
  26. No
  27. 25
  28. 89
  29. 36
  30. 120
  31. 23
  32. No
  33. 88
  34. 26
  35. 65
  36. 25
  37. 50
  38. 50
  39. 37
  40. 149

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