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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 464 · 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.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 30° and 24°. What is the exterior angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 110°. What is each of the other two angles (in degrees)?
  4. 4.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  5. 5.In triangle ABC, angle A = 65° and angle B = 36°. What is angle C (in degrees)?
  6. 6.Can a triangle have sides of 22 cm, 10 cm and 10 cm? (a) Yes (b) No
  7. 7.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  8. 8.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  9. 9.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  15. 15.Can a triangle have sides of 8 cm, 11 cm and 9 cm? (a) No (b) Yes
  16. 16.In triangle ABC, angle A = 71° and angle B = 64°. What is angle C (in degrees)?
  17. 17.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  18. 18.In triangle ABC, angle A = 68° and angle B = 76°. What is angle C (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  21. 21.Can a triangle have sides of 7 cm, 10 cm and 7 cm? (a) Yes (b) No
  22. 22.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 31° and 39°. What is the exterior angle (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 71° and 65°. What is the exterior angle (in degrees)?
  25. 25.In triangle ABC, angle A = 76° and angle B = 22°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 49° and angle B = 65°. What is angle C (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 58° and 66°. What is the exterior angle (in degrees)?
  29. 29.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)?
  30. 30.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  31. 31.An exterior angle of a triangle is 144°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  32. 32.In triangle ABC, angle A = 54° and angle B = 77°. What is angle C (in degrees)?
  33. 33.Can a triangle have sides of 7 cm, 9 cm and 19 cm? (a) Yes (b) No
  34. 34.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  35. 35.In triangle ABC, angle A = 88° and angle B = 53°. What is angle C (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 54° each. What is the third angle (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 22° and 30°. What is the exterior angle (in degrees)?
  38. 38.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 36° and 74°. What is the exterior angle (in degrees)?
  40. 40.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?

Answer key

  1. 70
  2. 54
  3. 35
  4. 72
  5. 79
  6. No
  7. 90
  8. 61
  9. 50
  10. 41
  11. 71
  12. 36
  13. 60
  14. 20
  15. Yes
  16. 45
  17. 33
  18. 36
  19. 134
  20. 15
  21. Yes
  22. 30
  23. 70
  24. 136
  25. 82
  26. 36
  27. 66
  28. 124
  29. 24
  30. 62
  31. 70
  32. 49
  33. No
  34. 25
  35. 39
  36. 72
  37. 52
  38. 76
  39. 110
  40. 24

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