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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 569 · 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.

NameDateTime takenScore ___ / 40
  1. 1.The two interior opposite angles of a triangle are 55° and 27°. What is the exterior angle (in degrees)?
  2. 2.In triangle ABC, angle A = 57° and angle B = 31°. What is angle C (in degrees)?
  3. 3.In triangle ABC, angle A = 78° and angle B = 22°. What is angle C (in degrees)?
  4. 4.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  5. 5.Can a triangle have sides of 13 cm, 7 cm and 10 cm? (a) Yes (b) No
  6. 6.In triangle ABC, angle A = 22° and angle B = 111°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 4 cm, 2 cm and 11 cm? (a) Yes (b) No
  9. 9.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 6 cm, 7 cm and 18 cm? (a) No (b) Yes
  12. 12.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 83° and angle B = 55°. What is angle C (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 50° and 24°. What is the exterior angle (in degrees)?
  15. 15.In triangle ABC, angle A = 47° and angle B = 83°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 92° and angle B = 55°. What is angle C (in degrees)?
  17. 17.An exterior angle of a triangle is 138°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  18. 18.Can a triangle have sides of 4 cm, 5 cm and 4 cm? (a) Yes (b) No
  19. 19.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  21. 21.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  23. 23.In triangle ABC, angle A = 89° and angle B = 30°. What is angle C (in degrees)?
  24. 24.An exterior angle of a triangle is 129°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  27. 27.In triangle ABC, angle A = 48° and angle B = 63°. What is angle C (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 52° and 43°. What is the exterior angle (in degrees)?
  30. 30.In triangle ABC, angle A = 93° and angle B = 35°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 80° and angle B = 30°. What is angle C (in degrees)?
  32. 32.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  33. 33.In triangle ABC, angle A = 90° and angle B = 21°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 11 cm, 9 cm and 10 cm? (a) Yes (b) No
  35. 35.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  36. 36.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)?
  37. 37.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 48° and angle B = 43°. What is angle C (in degrees)?
  39. 39.In triangle ABC, angle A = 74° and angle B = 23°. What is angle C (in degrees)?
  40. 40.In triangle ABC, angle A = 37° and angle B = 98°. What is angle C (in degrees)?

Answer key

  1. 82
  2. 92
  3. 80
  4. 12
  5. Yes
  6. 47
  7. 17
  8. No
  9. 54
  10. 75
  11. No
  12. 98
  13. 42
  14. 74
  15. 50
  16. 33
  17. 76
  18. Yes
  19. 120
  20. 26
  21. 22
  22. 5
  23. 61
  24. 59
  25. 69
  26. 100
  27. 69
  28. 44
  29. 95
  30. 52
  31. 70
  32. 40
  33. 69
  34. Yes
  35. 6
  36. 15
  37. 36
  38. 89
  39. 83
  40. 45

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