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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 985 · 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.An exterior angle of a triangle is 129°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  2. 2.An exterior angle of a triangle is 65°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  3. 3.In triangle ABC, angle A = 59° and angle B = 80°. What is angle C (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  5. 5.In triangle ABC, angle A = 69° and angle B = 45°. What is angle C (in degrees)?
  6. 6.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  8. 8.Can a triangle have sides of 6 cm, 19 cm and 9 cm? (a) No (b) Yes
  9. 9.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  10. 10.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  11. 11.In triangle ABC, angle A = 21° and angle B = 86°. What is angle C (in degrees)?
  12. 12.Can a triangle have sides of 6 cm, 18 cm and 12 cm? (a) Yes (b) No
  13. 13.Can a triangle have sides of 19 cm, 12 cm and 10 cm? (a) No (b) Yes
  14. 14.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  15. 15.Can a triangle have sides of 6 cm, 4 cm and 5 cm? (a) Yes (b) No
  16. 16.Can a triangle have sides of 13 cm, 6 cm and 7 cm? (a) Yes (b) No
  17. 17.Can a triangle have sides of 12 cm, 2 cm and 12 cm? (a) No (b) Yes
  18. 18.In triangle ABC, angle A = 54° and angle B = 51°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  20. 20.In triangle ABC, angle A = 39° and angle B = 31°. What is angle C (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 47° and 33°. What is the exterior angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 80° and 80°. What is the exterior angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 76° and 68°. What is the exterior angle (in degrees)?
  32. 32.In triangle ABC, angle A = 73° and angle B = 40°. What is angle C (in degrees)?
  33. 33.An exterior angle of a triangle is 133°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 72° each. What is the third angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 65° and 28°. What is the exterior angle (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 4 cm, 15 cm and 9 cm? (a) Yes (b) No
  39. 39.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 59° and 74°. What is the exterior angle (in degrees)?

Answer key

  1. 57
  2. 37
  3. 41
  4. 67
  5. 66
  6. 54
  7. 25
  8. No
  9. 20
  10. 7
  11. 73
  12. No
  13. Yes
  14. 43
  15. Yes
  16. No
  17. Yes
  18. 75
  19. 75
  20. 110
  21. 80
  22. 17
  23. 49
  24. 27
  25. 20
  26. 72
  27. 100
  28. 51
  29. 71
  30. 160
  31. 144
  32. 67
  33. 65
  34. 70
  35. 36
  36. 93
  37. 88
  38. No
  39. 53
  40. 133

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