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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 141 · 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 58°. What is the third angle (in degrees)?
  2. 2.Can a triangle have sides of 3 cm, 10 cm and 11 cm? (a) Yes (b) No
  3. 3.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 69° and 66°. What is the exterior angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  6. 6.Can a triangle have sides of 6 cm, 13 cm and 6 cm? (a) No (b) Yes
  7. 7.In triangle ABC, angle A = 59° and angle B = 72°. What is angle C (in degrees)?
  8. 8.Can a triangle have sides of 20 cm, 9 cm and 12 cm? (a) No (b) Yes
  9. 9.In triangle ABC, angle A = 61° and angle B = 66°. What is angle C (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 12 cm, 9 cm and 9 cm? (a) No (b) Yes
  12. 12.In triangle ABC, angle A = 43° and angle B = 80°. What is angle C (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  14. 14.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  16. 16.In triangle ABC, angle A = 30° and angle B = 107°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 54° and angle B = 47°. What is angle C (in degrees)?
  18. 18.Can a triangle have sides of 12 cm, 4 cm and 3 cm? (a) No (b) Yes
  19. 19.In triangle ABC, angle A = 60° and angle B = 54°. What is angle C (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  21. 21.Can a triangle have sides of 7 cm, 21 cm and 11 cm? (a) Yes (b) No
  22. 22.In triangle ABC, angle A = 70° and angle B = 36°. What is angle C (in degrees)?
  23. 23.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  24. 24.Can a triangle have sides of 7 cm, 11 cm and 22 cm? (a) Yes (b) No
  25. 25.Can a triangle have sides of 8 cm, 5 cm and 18 cm? (a) Yes (b) No
  26. 26.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  28. 28.In triangle ABC, angle A = 59° and angle B = 44°. What is angle C (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 31° and 43°. What is the exterior angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 20 cm, 6 cm and 11 cm? (a) Yes (b) No
  32. 32.Can a triangle have sides of 8 cm, 10 cm and 4 cm? (a) No (b) Yes
  33. 33.Can a triangle have sides of 6 cm, 15 cm and 6 cm? (a) No (b) Yes
  34. 34.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?
  35. 35.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  36. 36.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  37. 37.In triangle ABC, angle A = 53° and angle B = 21°. What is angle C (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 26° and 35°. What is the exterior angle (in degrees)?
  40. 40.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?

Answer key

  1. 32
  2. Yes
  3. 63
  4. 135
  5. 75
  6. No
  7. 49
  8. Yes
  9. 53
  10. 72
  11. Yes
  12. 57
  13. 52
  14. 47
  15. 17
  16. 43
  17. 79
  18. No
  19. 66
  20. 45
  21. No
  22. 74
  23. 44
  24. No
  25. No
  26. 42
  27. 58
  28. 77
  29. 74
  30. 31
  31. No
  32. Yes
  33. No
  34. 140
  35. 47
  36. 75
  37. 106
  38. 12
  39. 61
  40. 39

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