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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 43 · 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 angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  5. 5.In triangle ABC, angle A = 83° and angle B = 71°. What is angle C (in degrees)?
  6. 6.In triangle ABC, angle A = 22° and angle B = 91°. What is angle C (in degrees)?
  7. 7.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  9. 9.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  11. 11.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)?
  12. 12.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  13. 13.In triangle ABC, angle A = 55° and angle B = 42°. What is angle C (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 27° and 36°. What is the exterior angle (in degrees)?
  16. 16.Can a triangle have sides of 2 cm, 3 cm and 3 cm? (a) No (b) Yes
  17. 17.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 22° and 62°. What is the exterior angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 36° and 34°. What is the exterior angle (in degrees)?
  24. 24.In triangle ABC, angle A = 25° and angle B = 121°. What is angle C (in degrees)?
  25. 25.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  26. 26.In triangle ABC, angle A = 98° and angle B = 35°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 6 cm, 6 cm and 2 cm? (a) Yes (b) No
  28. 28.In triangle ABC, angle A = 45° and angle B = 54°. What is angle C (in degrees)?
  29. 29.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 33° and angle B = 37°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 32° and angle B = 76°. What is angle C (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?
  34. 34.An exterior angle of a triangle is 143°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  35. 35.Can a triangle have sides of 3 cm, 4 cm and 2 cm? (a) No (b) Yes
  36. 36.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  37. 37.In an isosceles triangle, the two equal angles are 44° each. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 3 cm, 2 cm and 2 cm? (a) Yes (b) No
  39. 39.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  40. 40.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?

Answer key

  1. 90
  2. 38
  3. 17
  4. 10
  5. 26
  6. 67
  7. 20
  8. 72
  9. 80
  10. 84
  11. 8
  12. 40
  13. 83
  14. 15
  15. 63
  16. Yes
  17. 45
  18. 12
  19. 126
  20. 20
  21. 84
  22. 50
  23. 70
  24. 34
  25. 40
  26. 47
  27. Yes
  28. 81
  29. 48
  30. 66
  31. 110
  32. 72
  33. 140
  34. 63
  35. Yes
  36. 24
  37. 92
  38. Yes
  39. 7
  40. 72

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