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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 972 · 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 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)?
  2. 2.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?
  4. 4.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  5. 5.In triangle ABC, angle A = 79° and angle B = 38°. What is angle C (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 41° and angle B = 114°. What is angle C (in degrees)?
  8. 8.Can a triangle have sides of 6 cm, 7 cm and 5 cm? (a) No (b) Yes
  9. 9.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 12 cm, 9 cm and 22 cm? (a) Yes (b) No
  11. 11.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  14. 14.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 61° each. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 2 cm, 3 cm and 2 cm? (a) Yes (b) No
  19. 19.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  20. 20.In triangle ABC, angle A = 42° and angle B = 73°. What is angle C (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 38° and 44°. What is the exterior angle (in degrees)?
  22. 22.Can a triangle have sides of 20 cm, 9 cm and 6 cm? (a) Yes (b) No
  23. 23.In triangle ABC, angle A = 90° and angle B = 47°. What is angle C (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  25. 25.In triangle ABC, angle A = 29° and angle B = 84°. What is angle C (in degrees)?
  26. 26.In triangle ABC, angle A = 81° and angle B = 53°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 83° and angle B = 35°. What is angle C (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 62° and 70°. What is the exterior angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 38° and 70°. What is the exterior angle (in degrees)?
  33. 33.In triangle ABC, angle A = 41° and angle B = 79°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 4 cm, 5 cm and 8 cm? (a) Yes (b) No
  35. 35.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  37. 37.In triangle ABC, angle A = 54° and angle B = 40°. What is angle C (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 80° and 30°. What is the exterior angle (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  40. 40.Can a triangle have sides of 4 cm, 13 cm and 9 cm? (a) Yes (b) No

Answer key

  1. 7
  2. 35
  3. 40
  4. 73
  5. 63
  6. 16
  7. 25
  8. Yes
  9. 90
  10. No
  11. 57
  12. 20
  13. 40
  14. 71
  15. 79
  16. 38
  17. 58
  18. Yes
  19. 40
  20. 65
  21. 82
  22. No
  23. 43
  24. 15
  25. 67
  26. 46
  27. 62
  28. 65
  29. 66
  30. 78
  31. 132
  32. 108
  33. 60
  34. Yes
  35. 45
  36. 100
  37. 86
  38. 110
  39. 25
  40. No

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