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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 928 · 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 a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  2. 2.In triangle ABC, angle A = 47° and angle B = 33°. What is angle C (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  4. 4.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  5. 5.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  7. 7.Can a triangle have sides of 11 cm, 21 cm and 10 cm? (a) No (b) Yes
  8. 8.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  9. 9.Can a triangle have sides of 3 cm, 11 cm and 9 cm? (a) Yes (b) No
  10. 10.In triangle ABC, angle A = 54° and angle B = 33°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 21° and angle B = 35°. What is angle C (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 26° and 74°. What is the exterior angle (in degrees)?
  13. 13.In triangle ABC, angle A = 21° and angle B = 102°. What is angle C (in degrees)?
  14. 14.Can a triangle have sides of 23 cm, 10 cm and 8 cm? (a) Yes (b) No
  15. 15.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  16. 16.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  17. 17.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 64°. What is each of the other two angles (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 76° and 44°. What is the exterior angle (in degrees)?
  21. 21.In triangle ABC, angle A = 96° and angle B = 33°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 86° and angle B = 44°. What is angle C (in degrees)?
  23. 23.Can a triangle have sides of 11 cm, 11 cm and 3 cm? (a) Yes (b) No
  24. 24.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  27. 27.In triangle ABC, angle A = 57° and angle B = 31°. What is angle C (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  29. 29.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 37° and angle B = 33°. What is angle C (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  34. 34.Can a triangle have sides of 9 cm, 5 cm and 8 cm? (a) Yes (b) No
  35. 35.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  36. 36.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  37. 37.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 92° and angle B = 26°. What is angle C (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 47° and 68°. What is the exterior angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?

Answer key

  1. 26
  2. 100
  3. 62
  4. 63
  5. 28
  6. 10
  7. No
  8. 15
  9. Yes
  10. 93
  11. 124
  12. 100
  13. 57
  14. No
  15. 73
  16. 48
  17. 12
  18. 58
  19. 47
  20. 120
  21. 51
  22. 50
  23. Yes
  24. 61
  25. 29
  26. 80
  27. 92
  28. 5
  29. 11
  30. 100
  31. 35
  32. 110
  33. 13
  34. Yes
  35. 68
  36. 18
  37. 20
  38. 62
  39. 115
  40. 57

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