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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 317 · 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 11°. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  5. 5.In triangle ABC, angle A = 40° and angle B = 90°. What is angle C (in degrees)?
  6. 6.In triangle ABC, angle A = 61° and angle B = 46°. What is angle C (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  8. 8.In triangle ABC, angle A = 96° and angle B = 43°. What is angle C (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 28° and 74°. What is the exterior angle (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 53° and 30°. What is the exterior angle (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 82° and angle B = 43°. What is angle C (in degrees)?
  14. 14.An exterior angle of a triangle is 120°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  16. 16.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  17. 17.In triangle ABC, angle A = 25° and angle B = 47°. What is angle C (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  19. 19.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  21. 21.Can a triangle have sides of 4 cm, 4 cm and 6 cm? (a) Yes (b) No
  22. 22.Can a triangle have sides of 3 cm, 2 cm and 2 cm? (a) Yes (b) No
  23. 23.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  24. 24.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  25. 25.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 97° and angle B = 32°. What is angle C (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 59° and 42°. What is the exterior angle (in degrees)?
  28. 28.In triangle ABC, angle A = 81° and angle B = 70°. What is angle C (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  30. 30.Can a triangle have sides of 9 cm, 22 cm and 12 cm? (a) No (b) Yes
  31. 31.Can a triangle have sides of 18 cm, 11 cm and 3 cm? (a) Yes (b) No
  32. 32.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  34. 34.In triangle ABC, angle A = 54° and angle B = 63°. What is angle C (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  36. 36.Can a triangle have sides of 14 cm, 5 cm and 7 cm? (a) No (b) Yes
  37. 37.Can a triangle have sides of 10 cm, 10 cm and 20 cm? (a) No (b) Yes
  38. 38.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  39. 39.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 23° and 48°. What is the exterior angle (in degrees)?

Answer key

  1. 79
  2. 48
  3. 90
  4. 100
  5. 50
  6. 73
  7. 30
  8. 41
  9. 102
  10. 19
  11. 83
  12. 110
  13. 55
  14. 61
  15. 28
  16. 50
  17. 108
  18. 124
  19. 55
  20. 32
  21. Yes
  22. Yes
  23. 69
  24. 12
  25. 88
  26. 51
  27. 101
  28. 29
  29. 73
  30. No
  31. No
  32. 40
  33. 84
  34. 63
  35. 21
  36. No
  37. No
  38. 20
  39. 45
  40. 71

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