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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 387 · 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 two interior opposite angles of a triangle are 77° and 32°. What is the exterior angle (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  3. 3.The two interior opposite angles of a triangle are 21° and 34°. What is the exterior angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 27° and 24°. What is the exterior angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 60° and 24°. What is the exterior angle (in degrees)?
  8. 8.Can a triangle have sides of 4 cm, 18 cm and 10 cm? (a) No (b) Yes
  9. 9.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 72° each. What is the third angle (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  12. 12.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  15. 15.Can a triangle have sides of 6 cm, 9 cm and 6 cm? (a) Yes (b) No
  16. 16.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?
  18. 18.An exterior angle of a triangle is 72°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  20. 20.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  22. 22.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 28° and angle B = 53°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 85° and angle B = 58°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 25° and angle B = 62°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 8 cm, 11 cm and 6 cm? (a) No (b) Yes
  29. 29.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  32. 32.Can a triangle have sides of 7 cm, 6 cm and 9 cm? (a) Yes (b) No
  33. 33.The two interior opposite angles of a triangle are 70° and 67°. What is the exterior angle (in degrees)?
  34. 34.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  35. 35.In triangle ABC, angle A = 69° and angle B = 68°. What is angle C (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 39° and 26°. What is the exterior angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 2 cm, 7 cm and 7 cm? (a) Yes (b) No
  39. 39.An exterior angle of a triangle is 65°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  40. 40.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?

Answer key

  1. 109
  2. 13
  3. 55
  4. 76
  5. 51
  6. 48
  7. 84
  8. No
  9. 69
  10. 36
  11. 25
  12. 31
  13. 120
  14. 45
  15. Yes
  16. 78
  17. 114
  18. 50
  19. 16
  20. 36
  21. 61
  22. 50
  23. 16
  24. 99
  25. 37
  26. 80
  27. 93
  28. Yes
  29. 64
  30. 77
  31. 90
  32. Yes
  33. 137
  34. 47
  35. 43
  36. 65
  37. 35
  38. Yes
  39. 25
  40. 3

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