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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 642 · 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 an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 44° each. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 5 cm, 6 cm and 5 cm? (a) Yes (b) No
  5. 5.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 17 cm, 11 cm and 10 cm? (a) Yes (b) No
  7. 7.Can a triangle have sides of 11 cm, 10 cm and 9 cm? (a) Yes (b) No
  8. 8.Can a triangle have sides of 11 cm, 12 cm and 3 cm? (a) No (b) Yes
  9. 9.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 12 cm, 12 cm and 3 cm? (a) No (b) Yes
  12. 12.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  13. 13.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  14. 14.In triangle ABC, angle A = 24° and angle B = 36°. What is angle C (in degrees)?
  15. 15.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 61° and angle B = 32°. What is angle C (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  19. 19.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 92° and angle B = 52°. What is angle C (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 14 cm, 9 cm and 8 cm? (a) No (b) Yes
  25. 25.In triangle ABC, angle A = 40° and angle B = 27°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  29. 29.Can a triangle have sides of 4 cm, 7 cm and 16 cm? (a) Yes (b) No
  30. 30.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 74° and angle B = 23°. What is angle C (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  37. 37.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 3 cm, 11 cm and 9 cm? (a) Yes (b) No

Answer key

  1. 90
  2. 92
  3. 14
  4. Yes
  5. 30
  6. Yes
  7. Yes
  8. Yes
  9. 120
  10. 72
  11. Yes
  12. 28
  13. 24
  14. 120
  15. 72
  16. 90
  17. 87
  18. 63
  19. 33
  20. 74
  21. 36
  22. 76
  23. 71
  24. Yes
  25. 113
  26. 20
  27. 68
  28. 20
  29. No
  30. 30
  31. 90
  32. 138
  33. 72
  34. 86
  35. 83
  36. 71
  37. 18
  38. 80
  39. 27
  40. Yes

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