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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 400 · 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 = 62° and angle B = 80°. What is angle C (in degrees)?
  2. 2.In triangle ABC, angle A = 27° and angle B = 83°. What is angle C (in degrees)?
  3. 3.In triangle ABC, angle A = 59° and angle B = 93°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 21° and 30°. What is the exterior angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  8. 8.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  9. 9.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  10. 10.An exterior angle of a triangle is 129°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 52° and 70°. What is the exterior angle (in degrees)?
  12. 12.In triangle ABC, angle A = 36° and angle B = 105°. What is angle C (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  15. 15.In triangle ABC, angle A = 23° and angle B = 103°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 33° and angle B = 21°. What is angle C (in degrees)?
  17. 17.Can a triangle have sides of 9 cm, 10 cm and 9 cm? (a) Yes (b) No
  18. 18.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  20. 20.In triangle ABC, angle A = 35° and angle B = 68°. What is angle C (in degrees)?
  21. 21.In triangle ABC, angle A = 51° and angle B = 100°. What is angle C (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 95° and angle B = 58°. What is angle C (in degrees)?
  24. 24.Can a triangle have sides of 2 cm, 11 cm and 7 cm? (a) Yes (b) No
  25. 25.An exterior angle of a triangle is 54°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  26. 26.Can a triangle have sides of 12 cm, 7 cm and 21 cm? (a) Yes (b) No
  27. 27.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  30. 30.Can a triangle have sides of 21 cm, 11 cm and 8 cm? (a) No (b) Yes
  31. 31.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  33. 33.Can a triangle have sides of 3 cm, 11 cm and 8 cm? (a) Yes (b) No
  34. 34.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  36. 36.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)?
  37. 37.Can a triangle have sides of 13 cm, 5 cm and 3 cm? (a) Yes (b) No
  38. 38.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  39. 39.Can a triangle have sides of 12 cm, 10 cm and 5 cm? (a) No (b) Yes
  40. 40.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?

Answer key

  1. 38
  2. 70
  3. 28
  4. 90
  5. 51
  6. 78
  7. 5
  8. 10
  9. 29
  10. 65
  11. 122
  12. 39
  13. 20
  14. 40
  15. 54
  16. 126
  17. Yes
  18. 62
  19. 20
  20. 77
  21. 29
  22. 42
  23. 27
  24. No
  25. 28
  26. No
  27. 65
  28. 67
  29. 65
  30. No
  31. 33
  32. 62
  33. No
  34. 51
  35. 20
  36. 7
  37. No
  38. 17
  39. Yes
  40. 60

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