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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 894 · 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 triangle ABC, angle A = 39° and angle B = 82°. What is angle C (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 47° and angle B = 69°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 35° and angle B = 30°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  9. 9.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  10. 10.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 35° and 59°. What is the exterior angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 69° and 23°. What is the exterior angle (in degrees)?
  15. 15.Can a triangle have sides of 12 cm, 8 cm and 23 cm? (a) No (b) Yes
  16. 16.The two interior opposite angles of a triangle are 58° and 77°. What is the exterior angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  21. 21.Can a triangle have sides of 7 cm, 7 cm and 6 cm? (a) Yes (b) No
  22. 22.Can a triangle have sides of 9 cm, 6 cm and 4 cm? (a) No (b) Yes
  23. 23.In triangle ABC, angle A = 35° and angle B = 89°. What is angle C (in degrees)?
  24. 24.Can a triangle have sides of 4 cm, 2 cm and 4 cm? (a) Yes (b) No
  25. 25.In an isosceles triangle, the two equal angles are 61° each. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 98° and angle B = 60°. What is angle C (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 158°. What is each of the other two angles (in degrees)?
  28. 28.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  29. 29.In triangle ABC, angle A = 24° and angle B = 105°. What is angle C (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  32. 32.Can a triangle have sides of 7 cm, 19 cm and 9 cm? (a) No (b) Yes
  33. 33.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 29° and 74°. What is the exterior angle (in degrees)?
  35. 35.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  36. 36.An exterior angle of a triangle is 43°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 30° and 40°. What is the exterior angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?

Answer key

  1. 59
  2. 64
  3. 72
  4. 48
  5. 71
  6. 64
  7. 115
  8. 80
  9. 12
  10. 104
  11. 94
  12. 90
  13. 73
  14. 92
  15. No
  16. 135
  17. 69
  18. 64
  19. 33
  20. 138
  21. Yes
  22. Yes
  23. 56
  24. Yes
  25. 58
  26. 22
  27. 11
  28. 40
  29. 51
  30. 17
  31. 22
  32. No
  33. 40
  34. 103
  35. 53
  36. 22
  37. 88
  38. 10
  39. 70
  40. 17

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