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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 378 · 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.

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  1. 1.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  3. 3.In triangle ABC, angle A = 33° and angle B = 85°. What is angle C (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 5 cm, 10 cm and 6 cm? (a) Yes (b) No
  9. 9.The two interior opposite angles of a triangle are 34° and 66°. What is the exterior angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  11. 11.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 76°. What is each of the other two angles (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 66° and 33°. What is the exterior angle (in degrees)?
  15. 15.In triangle ABC, angle A = 87° and angle B = 64°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 89° and angle B = 51°. What is angle C (in degrees)?
  17. 17.Can a triangle have sides of 11 cm, 17 cm and 7 cm? (a) No (b) Yes
  18. 18.In triangle ABC, angle A = 27° and angle B = 100°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  20. 20.Can a triangle have sides of 12 cm, 8 cm and 3 cm? (a) No (b) Yes
  21. 21.In triangle ABC, angle A = 28° and angle B = 120°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 56° and angle B = 31°. What is angle C (in degrees)?
  23. 23.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 57° and 74°. What is the exterior angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  27. 27.Can a triangle have sides of 10 cm, 23 cm and 9 cm? (a) Yes (b) No
  28. 28.Can a triangle have sides of 7 cm, 3 cm and 5 cm? (a) Yes (b) No
  29. 29.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  30. 30.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 74° and angle B = 75°. What is angle C (in degrees)?
  32. 32.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 6 cm, 4 cm and 6 cm? (a) No (b) Yes
  35. 35.Can a triangle have sides of 17 cm, 9 cm and 4 cm? (a) Yes (b) No
  36. 36.Can a triangle have sides of 11 cm, 9 cm and 15 cm? (a) No (b) Yes
  37. 37.In triangle ABC, angle A = 70° and angle B = 24°. What is angle C (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?

Answer key

  1. 20
  2. 17
  3. 62
  4. 50
  5. 30
  6. 37
  7. 16
  8. Yes
  9. 100
  10. 73
  11. 43
  12. 17
  13. 52
  14. 99
  15. 29
  16. 40
  17. Yes
  18. 53
  19. 84
  20. No
  21. 32
  22. 93
  23. 68
  24. 76
  25. 131
  26. 75
  27. No
  28. Yes
  29. 12
  30. 11
  31. 31
  32. 59
  33. 132
  34. Yes
  35. No
  36. Yes
  37. 86
  38. 94
  39. 51
  40. 26

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