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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 668 · 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 shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  2. 2.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 36° and 76°. What is the exterior angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  5. 5.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  6. 6.In triangle ABC, angle A = 47° and angle B = 35°. 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.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 75° and 59°. What is the exterior angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  14. 14.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  15. 15.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  16. 16.Can a triangle have sides of 3 cm, 6 cm and 6 cm? (a) No (b) Yes
  17. 17.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  20. 20.In triangle ABC, angle A = 36° and angle B = 60°. What is angle C (in degrees)?
  21. 21.In triangle ABC, angle A = 35° and angle B = 48°. What is angle C (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 58° and 20°. What is the exterior angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 12 cm, 11 cm and 6 cm? (a) No (b) Yes
  26. 26.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 25° and 59°. What is the exterior angle (in degrees)?
  28. 28.Can a triangle have sides of 14 cm, 9 cm and 3 cm? (a) Yes (b) No
  29. 29.Can a triangle have sides of 2 cm, 6 cm and 12 cm? (a) No (b) Yes
  30. 30.Can a triangle have sides of 7 cm, 12 cm and 10 cm? (a) No (b) Yes
  31. 31.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  33. 33.In triangle ABC, angle A = 75° and angle B = 64°. What is angle C (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 29° and 36°. What is the exterior angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 27° and 32°. What is the exterior angle (in degrees)?
  37. 37.In triangle ABC, angle A = 36° and angle B = 107°. What is angle C (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  40. 40.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?

Answer key

  1. 25
  2. 36
  3. 112
  4. 74
  5. 8
  6. 98
  7. 30
  8. 25
  9. 90
  10. 134
  11. 40
  12. 100
  13. 41
  14. 9
  15. 11
  16. Yes
  17. 84
  18. 74
  19. 75
  20. 84
  21. 97
  22. 79
  23. 78
  24. 61
  25. Yes
  26. 59
  27. 84
  28. No
  29. No
  30. Yes
  31. 45
  32. 69
  33. 41
  34. 28
  35. 65
  36. 59
  37. 37
  38. 120
  39. 49
  40. 44

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