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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 321 · 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 67°. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  4. 4.An exterior angle of a triangle is 43°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  6. 6.The two interior opposite angles of a triangle are 78° and 67°. What is the exterior angle (in degrees)?
  7. 7.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)?
  8. 8.Can a triangle have sides of 4 cm, 2 cm and 9 cm? (a) No (b) Yes
  9. 9.Can a triangle have sides of 11 cm, 3 cm and 3 cm? (a) No (b) Yes
  10. 10.In triangle ABC, angle A = 22° and angle B = 61°. What is angle C (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  12. 12.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 71° and 41°. What is the exterior angle (in degrees)?
  14. 14.In triangle ABC, angle A = 87° and angle B = 46°. What is angle C (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 68° and 32°. What is the exterior angle (in degrees)?
  16. 16.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  17. 17.Can a triangle have sides of 9 cm, 5 cm and 7 cm? (a) No (b) Yes
  18. 18.In triangle ABC, angle A = 99° and angle B = 20°. What is angle C (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  21. 21.In triangle ABC, angle A = 54° and angle B = 38°. What is angle C (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  23. 23.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  24. 24.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 49° and 27°. What is the exterior angle (in degrees)?
  26. 26.Can a triangle have sides of 6 cm, 14 cm and 11 cm? (a) No (b) Yes
  27. 27.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  29. 29.Can a triangle have sides of 9 cm, 4 cm and 2 cm? (a) No (b) Yes
  30. 30.In triangle ABC, angle A = 82° and angle B = 77°. What is angle C (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 75° and 23°. What is the exterior angle (in degrees)?
  32. 32.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  33. 33.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  34. 34.In triangle ABC, angle A = 53° and angle B = 35°. What is angle C (in degrees)?
  35. 35.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  36. 36.In triangle ABC, angle A = 51° and angle B = 55°. What is angle C (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 25° and 29°. What is the exterior angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  39. 39.Can a triangle have sides of 7 cm, 10 cm and 20 cm? (a) Yes (b) No
  40. 40.The two interior opposite angles of a triangle are 54° and 52°. What is the exterior angle (in degrees)?

Answer key

  1. 23
  2. 66
  3. 31
  4. 21
  5. 25
  6. 145
  7. 10
  8. No
  9. No
  10. 97
  11. 11
  12. 22
  13. 112
  14. 47
  15. 100
  16. 18
  17. Yes
  18. 61
  19. 64
  20. 45
  21. 88
  22. 13
  23. 24
  24. 50
  25. 76
  26. Yes
  27. 18
  28. 90
  29. No
  30. 21
  31. 98
  32. 20
  33. 75
  34. 92
  35. 76
  36. 74
  37. 54
  38. 55
  39. No
  40. 106

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