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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 743 · 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 80° and 44°. What is the exterior angle (in degrees)?
  2. 2.In triangle ABC, angle A = 40° and angle B = 87°. What is angle C (in degrees)?
  3. 3.In triangle ABC, angle A = 80° and angle B = 62°. What is angle C (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 76° each. What is the third angle (in degrees)?
  5. 5.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  6. 6.Can a triangle have sides of 3 cm, 9 cm and 17 cm? (a) No (b) Yes
  7. 7.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  11. 11.In triangle ABC, angle A = 58° and angle B = 37°. What is angle C (in degrees)?
  12. 12.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 47° and 24°. What is the exterior angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 83° and angle B = 67°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  21. 21.Can a triangle have sides of 3 cm, 11 cm and 15 cm? (a) No (b) Yes
  22. 22.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  23. 23.Can a triangle have sides of 6 cm, 11 cm and 11 cm? (a) No (b) Yes
  24. 24.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  25. 25.In triangle ABC, angle A = 55° and angle B = 93°. What is angle C (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 43° and 21°. What is the exterior angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  28. 28.Can a triangle have sides of 12 cm, 8 cm and 6 cm? (a) Yes (b) No
  29. 29.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 40° and angle B = 21°. What is angle C (in degrees)?
  32. 32.Can a triangle have sides of 8 cm, 8 cm and 5 cm? (a) No (b) Yes
  33. 33.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  37. 37.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  38. 38.Can a triangle have sides of 2 cm, 8 cm and 4 cm? (a) Yes (b) No
  39. 39.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  40. 40.An exterior angle of a triangle is 58°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?

Answer key

  1. 124
  2. 53
  3. 38
  4. 28
  5. 44
  6. No
  7. 84
  8. 59
  9. 20
  10. 10
  11. 85
  12. 39
  13. 71
  14. 36
  15. 35
  16. 11
  17. 65
  18. 30
  19. 40
  20. 39
  21. No
  22. 50
  23. Yes
  24. 32
  25. 32
  26. 64
  27. 75
  28. Yes
  29. 77
  30. 17
  31. 119
  32. Yes
  33. 90
  34. 90
  35. 36
  36. 18
  37. 41
  38. No
  39. 130
  40. 28

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