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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 807 · 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 64°. What is the third angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 26° and 70°. What is the exterior angle (in degrees)?
  3. 3.In triangle ABC, angle A = 85° and angle B = 39°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  6. 6.In triangle ABC, angle A = 34° and angle B = 42°. What is angle C (in degrees)?
  7. 7.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  8. 8.In triangle ABC, angle A = 36° and angle B = 38°. What is angle C (in degrees)?
  9. 9.Can a triangle have sides of 6 cm, 7 cm and 6 cm? (a) Yes (b) No
  10. 10.In triangle ABC, angle A = 43° and angle B = 28°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 39° and angle B = 42°. What is angle C (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  14. 14.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  15. 15.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  18. 18.Can a triangle have sides of 4 cm, 3 cm and 2 cm? (a) No (b) Yes
  19. 19.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 26° and 30°. What is the exterior angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  23. 23.In triangle ABC, angle A = 80° and angle B = 59°. What is angle C (in degrees)?
  24. 24.Can a triangle have sides of 2 cm, 6 cm and 3 cm? (a) Yes (b) No
  25. 25.The two interior opposite angles of a triangle are 67° and 54°. What is the exterior angle (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  27. 27.In triangle ABC, angle A = 47° and angle B = 94°. What is angle C (in degrees)?
  28. 28.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  31. 31.In triangle ABC, angle A = 23° and angle B = 40°. What is angle C (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  33. 33.The two interior opposite angles of a triangle are 57° and 49°. What is the exterior angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?
  37. 37.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)?
  38. 38.The two interior opposite angles of a triangle are 20° and 49°. What is the exterior angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 71° and 61°. What is the exterior angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?

Answer key

  1. 26
  2. 96
  3. 56
  4. 90
  5. 5
  6. 104
  7. 64
  8. 106
  9. Yes
  10. 109
  11. 99
  12. 49
  13. 25
  14. 52
  15. 54
  16. 59
  17. 12
  18. Yes
  19. 67
  20. 16
  21. 56
  22. 120
  23. 41
  24. No
  25. 121
  26. 62
  27. 39
  28. 34
  29. 34
  30. 70
  31. 117
  32. 15
  33. 106
  34. 50
  35. 100
  36. 79
  37. 8
  38. 69
  39. 132
  40. 90

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