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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 521 · 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 94°. What is each of the other two angles (in degrees)?
  2. 2.In triangle ABC, angle A = 32° and angle B = 20°. What is angle C (in degrees)?
  3. 3.In triangle ABC, angle A = 69° and angle B = 51°. What is angle C (in degrees)?
  4. 4.Can a triangle have sides of 21 cm, 8 cm and 10 cm? (a) No (b) Yes
  5. 5.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  7. 7.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)?
  8. 8.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  9. 9.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  10. 10.In triangle ABC, angle A = 39° and angle B = 77°. What is angle C (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  12. 12.Can a triangle have sides of 12 cm, 14 cm and 6 cm? (a) Yes (b) No
  13. 13.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  17. 17.In triangle ABC, angle A = 32° and angle B = 29°. What is angle C (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 66° and 47°. What is the exterior angle (in degrees)?
  19. 19.An exterior angle of a triangle is 64°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 94° and angle B = 36°. What is angle C (in degrees)?
  22. 22.An exterior angle of a triangle is 129°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  23. 23.In triangle ABC, angle A = 79° and angle B = 43°. What is angle C (in degrees)?
  24. 24.Can a triangle have sides of 4 cm, 5 cm and 3 cm? (a) No (b) Yes
  25. 25.Can a triangle have sides of 2 cm, 8 cm and 2 cm? (a) No (b) Yes
  26. 26.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 60° and angle B = 78°. What is angle C (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 45° and 24°. What is the exterior angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 76° and 65°. What is the exterior angle (in degrees)?
  33. 33.Can a triangle have sides of 11 cm, 9 cm and 23 cm? (a) No (b) Yes
  34. 34.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 23° and 66°. What is the exterior angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  37. 37.In triangle ABC, angle A = 39° and angle B = 63°. What is angle C (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?

Answer key

  1. 43
  2. 128
  3. 60
  4. No
  5. 20
  6. 22
  7. 24
  8. 77
  9. 33
  10. 64
  11. 69
  12. Yes
  13. 72
  14. 73
  15. 20
  16. 17
  17. 119
  18. 113
  19. 39
  20. 77
  21. 50
  22. 54
  23. 58
  24. Yes
  25. No
  26. 10
  27. 42
  28. 69
  29. 52
  30. 40
  31. 80
  32. 141
  33. No
  34. 67
  35. 89
  36. 34
  37. 78
  38. 42
  39. 18
  40. 51

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