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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 632 · 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 a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  2. 2.In triangle ABC, angle A = 82° and angle B = 28°. What is angle C (in degrees)?
  3. 3.In triangle ABC, angle A = 39° and angle B = 82°. What is angle C (in degrees)?
  4. 4.In triangle ABC, angle A = 41° and angle B = 66°. What is angle C (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 94° and angle B = 25°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 38° and angle B = 96°. What is angle C (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  10. 10.In triangle ABC, angle A = 86° and angle B = 26°. What is angle C (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  14. 14.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 33° and 48°. What is the exterior angle (in degrees)?
  16. 16.In triangle ABC, angle A = 21° and angle B = 24°. What is angle C (in degrees)?
  17. 17.Can a triangle have sides of 11 cm, 7 cm and 10 cm? (a) No (b) Yes
  18. 18.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  20. 20.In triangle ABC, angle A = 64° and angle B = 55°. What is angle C (in degrees)?
  21. 21.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  22. 22.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  24. 24.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)?
  25. 25.The two interior opposite angles of a triangle are 67° and 65°. What is the exterior angle (in degrees)?
  26. 26.In triangle ABC, angle A = 49° and angle B = 50°. What is angle C (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  28. 28.In triangle ABC, angle A = 70° and angle B = 26°. What is angle C (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 62° and 78°. What is the exterior angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  34. 34.In triangle ABC, angle A = 73° and angle B = 56°. What is angle C (in degrees)?
  35. 35.Can a triangle have sides of 11 cm, 2 cm and 11 cm? (a) Yes (b) No
  36. 36.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  37. 37.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  38. 38.Can a triangle have sides of 3 cm, 5 cm and 4 cm? (a) No (b) Yes
  39. 39.Can a triangle have sides of 10 cm, 10 cm and 20 cm? (a) No (b) Yes
  40. 40.Can a triangle have sides of 10 cm, 11 cm and 10 cm? (a) Yes (b) No

Answer key

  1. 51
  2. 70
  3. 59
  4. 73
  5. 53
  6. 34
  7. 61
  8. 46
  9. 45
  10. 68
  11. 74
  12. 30
  13. 75
  14. 24
  15. 81
  16. 135
  17. Yes
  18. 37
  19. 120
  20. 61
  21. 56
  22. 70
  23. 18
  24. 8
  25. 132
  26. 81
  27. 17
  28. 84
  29. 140
  30. 100
  31. 54
  32. 40
  33. 13
  34. 51
  35. Yes
  36. 58
  37. 38
  38. Yes
  39. No
  40. Yes

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