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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 953 · 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 15°. What is the third angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 77° and 70°. What is the exterior angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 30° and 24°. What is the exterior angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  11. 11.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 54° and 41°. What is the exterior angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 29° and 70°. What is the exterior angle (in degrees)?
  15. 15.Can a triangle have sides of 9 cm, 15 cm and 5 cm? (a) No (b) Yes
  16. 16.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 90° and angle B = 42°. What is angle C (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 61° and 27°. What is the exterior angle (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 67° and 57°. What is the exterior angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  22. 22.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  24. 24.Can a triangle have sides of 11 cm, 11 cm and 2 cm? (a) Yes (b) No
  25. 25.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 60° and angle B = 95°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 74° and angle B = 24°. What is angle C (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 43° and 80°. What is the exterior angle (in degrees)?
  29. 29.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  30. 30.In triangle ABC, angle A = 87° and angle B = 35°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 66° and angle B = 31°. What is angle C (in degrees)?
  32. 32.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 7 cm, 18 cm and 11 cm? (a) Yes (b) No
  35. 35.In triangle ABC, angle A = 90° and angle B = 53°. What is angle C (in degrees)?
  36. 36.Can a triangle have sides of 15 cm, 12 cm and 7 cm? (a) Yes (b) No
  37. 37.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 12 cm, 14 cm and 6 cm? (a) Yes (b) No
  39. 39.Can a triangle have sides of 8 cm, 13 cm and 4 cm? (a) Yes (b) No
  40. 40.In triangle ABC, angle A = 43° and angle B = 39°. What is angle C (in degrees)?

Answer key

  1. 75
  2. 54
  3. 90
  4. 26
  5. 120
  6. 147
  7. 72
  8. 30
  9. 54
  10. 13
  11. 27
  12. 95
  13. 100
  14. 99
  15. No
  16. 20
  17. 48
  18. 88
  19. 17
  20. 124
  21. 36
  22. 27
  23. 25
  24. Yes
  25. 100
  26. 25
  27. 82
  28. 123
  29. 60
  30. 58
  31. 83
  32. 25
  33. 55
  34. No
  35. 37
  36. Yes
  37. 42
  38. Yes
  39. No
  40. 98

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