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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 715 · 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.In triangle ABC, angle A = 97° and angle B = 26°. What is angle C (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 = 25° and angle B = 34°. What is angle C (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  6. 6.An exterior angle of a triangle is 136°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 34° and 58°. What is the exterior angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  9. 9.Can a triangle have sides of 8 cm, 6 cm and 10 cm? (a) No (b) Yes
  10. 10.In triangle ABC, angle A = 48° and angle B = 24°. What is angle C (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  12. 12.Can a triangle have sides of 5 cm, 7 cm and 9 cm? (a) No (b) Yes
  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 two interior opposite angles of a triangle are 58° and 67°. What is the exterior angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?
  16. 16.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  17. 17.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 63° and 51°. What is the exterior angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  22. 22.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)?
  23. 23.In triangle ABC, angle A = 31° and angle B = 113°. What is angle C (in degrees)?
  24. 24.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 79° and angle B = 66°. What is angle C (in degrees)?
  27. 27.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  28. 28.An exterior angle of a triangle is 120°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 40° and 36°. What is the exterior angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  32. 32.Can a triangle have sides of 10 cm, 2 cm and 7 cm? (a) Yes (b) No
  33. 33.Can a triangle have sides of 8 cm, 8 cm and 14 cm? (a) No (b) Yes
  34. 34.In triangle ABC, angle A = 33° and angle B = 111°. What is angle C (in degrees)?
  35. 35.Can a triangle have sides of 19 cm, 8 cm and 7 cm? (a) Yes (b) No
  36. 36.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 47° and 20°. What is the exterior angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 11 cm, 3 cm and 10 cm? (a) No (b) Yes

Answer key

  1. 57
  2. 17
  3. 121
  4. 128
  5. 20
  6. 76
  7. 92
  8. 63
  9. Yes
  10. 108
  11. 25
  12. Yes
  13. 72
  14. 125
  15. 96
  16. 7
  17. 20
  18. 22
  19. 80
  20. 114
  21. 23
  22. 10
  23. 36
  24. 36
  25. 40
  26. 35
  27. 72
  28. 58
  29. 57
  30. 76
  31. 100
  32. No
  33. Yes
  34. 36
  35. No
  36. 51
  37. 67
  38. 45
  39. 27
  40. Yes

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