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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 565 · 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 = 29° and angle B = 100°. What is angle C (in degrees)?
  2. 2.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  3. 3.Can a triangle have sides of 7 cm, 20 cm and 12 cm? (a) Yes (b) No
  4. 4.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  5. 5.In triangle ABC, angle A = 85° and angle B = 51°. What is angle C (in degrees)?
  6. 6.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  7. 7.Can a triangle have sides of 10 cm, 10 cm and 20 cm? (a) Yes (b) No
  8. 8.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  9. 9.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)?
  10. 10.Can a triangle have sides of 10 cm, 22 cm and 9 cm? (a) No (b) Yes
  11. 11.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  12. 12.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  13. 13.In triangle ABC, angle A = 40° and angle B = 115°. What is angle C (in degrees)?
  14. 14.In triangle ABC, angle A = 20° and angle B = 37°. What is angle C (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  16. 16.In triangle ABC, angle A = 99° and angle B = 38°. What is angle C (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 30° and 62°. What is the exterior angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 4 cm, 11 cm and 2 cm? (a) Yes (b) No
  26. 26.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  27. 27.In triangle ABC, angle A = 92° and angle B = 27°. What is angle C (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (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.Can a triangle have sides of 7 cm, 8 cm and 9 cm? (a) Yes (b) No
  31. 31.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  32. 32.Can a triangle have sides of 6 cm, 6 cm and 13 cm? (a) No (b) Yes
  33. 33.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  38. 38.In triangle ABC, angle A = 99° and angle B = 46°. What is angle C (in degrees)?
  39. 39.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  40. 40.Can a triangle have sides of 5 cm, 3 cm and 9 cm? (a) Yes (b) No

Answer key

  1. 51
  2. 39
  3. No
  4. 35
  5. 44
  6. 84
  7. No
  8. 50
  9. 24
  10. No
  11. 77
  12. 15
  13. 25
  14. 123
  15. 61
  16. 43
  17. 90
  18. 90
  19. 92
  20. 51
  21. 136
  22. 76
  23. 118
  24. 51
  25. No
  26. 20
  27. 61
  28. 59
  29. 48
  30. Yes
  31. 18
  32. No
  33. 84
  34. 37
  35. 78
  36. 44
  37. 10
  38. 35
  39. 57
  40. No

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