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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 517 · 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 3 : 4 : 5. What is the smallest angle (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 24° and angle B = 45°. What is angle C (in degrees)?
  5. 5.In triangle ABC, angle A = 30° and angle B = 82°. What is angle C (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 34° and 56°. What is the exterior angle (in degrees)?
  7. 7.In triangle ABC, angle A = 67° and angle B = 32°. What is angle C (in degrees)?
  8. 8.Can a triangle have sides of 5 cm, 7 cm and 11 cm? (a) No (b) Yes
  9. 9.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 86° and angle B = 41°. What is angle C (in degrees)?
  11. 11.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  12. 12.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  13. 13.In triangle ABC, angle A = 50° and angle B = 103°. What is angle C (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  17. 17.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  18. 18.In triangle ABC, angle A = 39° and angle B = 97°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 66° and angle B = 87°. What is angle C (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  25. 25.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  26. 26.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  28. 28.In triangle ABC, angle A = 24° and angle B = 39°. What is angle C (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  30. 30.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 70° and 28°. What is the exterior angle (in degrees)?
  32. 32.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 3 cm, 16 cm and 8 cm? (a) No (b) Yes
  35. 35.In triangle ABC, angle A = 75° and angle B = 29°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 84° and angle B = 41°. What is angle C (in degrees)?
  37. 37.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 76° and 30°. What is the exterior angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 69° and 31°. What is the exterior angle (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?

Answer key

  1. 45
  2. 30
  3. 28
  4. 111
  5. 68
  6. 90
  7. 81
  8. Yes
  9. 78
  10. 53
  11. 36
  12. 17
  13. 27
  14. 62
  15. 74
  16. 100
  17. 24
  18. 44
  19. 27
  20. 67
  21. 50
  22. 23
  23. 30
  24. 71
  25. 75
  26. 63
  27. 56
  28. 117
  29. 26
  30. 22
  31. 98
  32. 71
  33. 64
  34. No
  35. 76
  36. 55
  37. 120
  38. 106
  39. 100
  40. 122

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