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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 104 · 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 36° and 30°. What is the exterior angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  4. 4.In triangle ABC, angle A = 83° and angle B = 24°. What is angle C (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  6. 6.Can a triangle have sides of 15 cm, 6 cm and 10 cm? (a) No (b) Yes
  7. 7.In triangle ABC, angle A = 100° and angle B = 31°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 74° and angle B = 51°. What is angle C (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  11. 11.Can a triangle have sides of 17 cm, 8 cm and 7 cm? (a) No (b) Yes
  12. 12.Can a triangle have sides of 3 cm, 2 cm and 4 cm? (a) No (b) Yes
  13. 13.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  14. 14.Can a triangle have sides of 12 cm, 15 cm and 2 cm? (a) No (b) Yes
  15. 15.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  21. 21.In triangle ABC, angle A = 41° and angle B = 89°. What is angle C (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 10 cm, 10 cm and 22 cm? (a) No (b) Yes
  25. 25.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  26. 26.An exterior angle of a triangle is 46°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  27. 27.Can a triangle have sides of 10 cm, 14 cm and 10 cm? (a) Yes (b) No
  28. 28.In triangle ABC, angle A = 99° and angle B = 37°. What is angle C (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  30. 30.Can a triangle have sides of 9 cm, 3 cm and 3 cm? (a) Yes (b) No
  31. 31.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  32. 32.Can a triangle have sides of 7 cm, 11 cm and 3 cm? (a) Yes (b) No
  33. 33.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 26° and angle B = 57°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 60° and angle B = 69°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  38. 38.In triangle ABC, angle A = 85° and angle B = 53°. What is angle C (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 67° and 77°. What is the exterior angle (in degrees)?
  40. 40.In triangle ABC, angle A = 35° and angle B = 112°. What is angle C (in degrees)?

Answer key

  1. 66
  2. 33
  3. 36
  4. 73
  5. 20
  6. Yes
  7. 49
  8. 55
  9. 20
  10. 54
  11. No
  12. Yes
  13. 128
  14. No
  15. 36
  16. 24
  17. 49
  18. 46
  19. 37
  20. 30
  21. 50
  22. 55
  23. 34
  24. No
  25. 67
  26. 26
  27. Yes
  28. 44
  29. 18
  30. No
  31. 20
  32. No
  33. 72
  34. 29
  35. 97
  36. 51
  37. 39
  38. 42
  39. 144
  40. 33

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