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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 244 · 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 50° and 78°. What is the exterior angle (in degrees)?
  2. 2.In triangle ABC, angle A = 43° and angle B = 108°. What is angle C (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  4. 4.In triangle ABC, angle A = 86° and angle B = 32°. What is angle C (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  6. 6.In triangle ABC, angle A = 41° and angle B = 86°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 27° and angle B = 40°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 22° and angle B = 85°. What is angle C (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 22° and 48°. What is the exterior angle (in degrees)?
  10. 10.An exterior angle of a triangle is 155°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  11. 11.Can a triangle have sides of 18 cm, 4 cm and 12 cm? (a) No (b) Yes
  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 a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  14. 14.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)?
  15. 15.Can a triangle have sides of 2 cm, 10 cm and 10 cm? (a) No (b) Yes
  16. 16.In triangle ABC, angle A = 28° and angle B = 107°. What is angle C (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  18. 18.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 33° and angle B = 118°. What is angle C (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 86°. What is each of the other two angles (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  25. 25.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 9 cm, 18 cm and 9 cm? (a) Yes (b) No
  27. 27.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 64° and angle B = 32°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 93° and angle B = 31°. What is angle C (in degrees)?
  32. 32.Can a triangle have sides of 22 cm, 12 cm and 5 cm? (a) Yes (b) No
  33. 33.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  37. 37.Can a triangle have sides of 9 cm, 7 cm and 10 cm? (a) No (b) Yes
  38. 38.In triangle ABC, angle A = 38° and angle B = 104°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?

Answer key

  1. 128
  2. 29
  3. 25
  4. 62
  5. 90
  6. 53
  7. 113
  8. 73
  9. 70
  10. 77
  11. No
  12. 67
  13. 72
  14. 15
  15. Yes
  16. 45
  17. 13
  18. 31
  19. 116
  20. 43
  21. 29
  22. 30
  23. 47
  24. 17
  25. 110
  26. No
  27. 15
  28. 136
  29. 51
  30. 84
  31. 56
  32. No
  33. 19
  34. 20
  35. 128
  36. 30
  37. Yes
  38. 38
  39. 34
  40. 56

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