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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 318 · 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 a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 70° and 64°. What is the exterior angle (in degrees)?
  3. 3.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  4. 4.In triangle ABC, angle A = 81° and angle B = 47°. What is angle C (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  6. 6.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  7. 7.In triangle ABC, angle A = 55° and angle B = 79°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 42° and 62°. What is the exterior angle (in degrees)?
  10. 10.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)?
  11. 11.In triangle ABC, angle A = 87° and angle B = 23°. What is angle C (in degrees)?
  12. 12.Can a triangle have sides of 11 cm, 2 cm and 10 cm? (a) No (b) Yes
  13. 13.Can a triangle have sides of 4 cm, 8 cm and 4 cm? (a) No (b) Yes
  14. 14.Can a triangle have sides of 1 cm, 3 cm and 3 cm? (a) No (b) Yes
  15. 15.In triangle ABC, angle A = 76° and angle B = 24°. What is angle C (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  17. 17.Can a triangle have sides of 22 cm, 12 cm and 7 cm? (a) No (b) Yes
  18. 18.Can a triangle have sides of 8 cm, 8 cm and 16 cm? (a) No (b) Yes
  19. 19.In an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?
  20. 20.In triangle ABC, angle A = 22° and angle B = 20°. What is angle C (in degrees)?
  21. 21.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  23. 23.Can a triangle have sides of 8 cm, 10 cm and 5 cm? (a) Yes (b) No
  24. 24.In triangle ABC, angle A = 22° and angle B = 28°. What is angle C (in degrees)?
  25. 25.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  26. 26.An exterior angle of a triangle is 134°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 79° and 46°. What is the exterior angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 53° and 78°. What is the exterior angle (in degrees)?
  30. 30.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  31. 31.Can a triangle have sides of 10 cm, 24 cm and 10 cm? (a) No (b) Yes
  32. 32.The two interior opposite angles of a triangle are 33° and 40°. What is the exterior angle (in degrees)?
  33. 33.In triangle ABC, angle A = 53° and angle B = 62°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 96° and angle B = 50°. What is angle C (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  36. 36.In triangle ABC, angle A = 41° and angle B = 101°. What is angle C (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 80° and 53°. What is the exterior angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 25° and 42°. What is the exterior angle (in degrees)?
  40. 40.In triangle ABC, angle A = 44° and angle B = 80°. What is angle C (in degrees)?

Answer key

  1. 78
  2. 134
  3. 15
  4. 52
  5. 39
  6. 15
  7. 46
  8. 72
  9. 104
  10. 24
  11. 70
  12. Yes
  13. No
  14. Yes
  15. 80
  16. 69
  17. No
  18. No
  19. 38
  20. 138
  21. 75
  22. 66
  23. Yes
  24. 130
  25. 40
  26. 70
  27. 125
  28. 100
  29. 131
  30. 12
  31. No
  32. 73
  33. 65
  34. 34
  35. 25
  36. 38
  37. 133
  38. 90
  39. 67
  40. 56

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