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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 670 · 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 90°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  3. 3.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 14 cm, 2 cm and 8 cm? (a) No (b) Yes
  5. 5.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  6. 6.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  7. 7.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  9. 9.Can a triangle have sides of 5 cm, 4 cm and 2 cm? (a) Yes (b) No
  10. 10.In triangle ABC, angle A = 56° and angle B = 24°. What is angle C (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  12. 12.In triangle ABC, angle A = 75° and angle B = 40°. What is angle C (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 53° and 44°. What is the exterior angle (in degrees)?
  14. 14.In triangle ABC, angle A = 75° and angle B = 36°. What is angle C (in degrees)?
  15. 15.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  16. 16.Can a triangle have sides of 11 cm, 9 cm and 15 cm? (a) No (b) Yes
  17. 17.Can a triangle have sides of 11 cm, 10 cm and 9 cm? (a) No (b) Yes
  18. 18.In an isosceles triangle, the two equal angles are 55° each. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 52° and angle B = 54°. What is angle C (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  21. 21.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  23. 23.Can a triangle have sides of 2 cm, 3 cm and 3 cm? (a) Yes (b) No
  24. 24.Can a triangle have sides of 17 cm, 8 cm and 12 cm? (a) No (b) Yes
  25. 25.In triangle ABC, angle A = 29° and angle B = 49°. What is angle C (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 72° and 32°. What is the exterior angle (in degrees)?
  28. 28.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third 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 : 7 : 9. What is the biggest angle (in degrees)?
  31. 31.In triangle ABC, angle A = 53° and angle B = 95°. What is angle C (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  35. 35.An exterior angle of a triangle is 140°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  36. 36.An exterior angle of a triangle is 131°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 64° and 59°. What is the exterior angle (in degrees)?
  38. 38.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  39. 39.In triangle ABC, angle A = 41° and angle B = 94°. What is angle C (in degrees)?
  40. 40.In triangle ABC, angle A = 36° and angle B = 111°. What is angle C (in degrees)?

Answer key

  1. 48
  2. 30
  3. 21
  4. No
  5. 59
  6. 3
  7. 36
  8. 18
  9. Yes
  10. 100
  11. 90
  12. 65
  13. 97
  14. 69
  15. 79
  16. Yes
  17. Yes
  18. 70
  19. 74
  20. 25
  21. 35
  22. 16
  23. Yes
  24. Yes
  25. 102
  26. 60
  27. 104
  28. 36
  29. 11
  30. 90
  31. 32
  32. 52
  33. 50
  34. 18
  35. 68
  36. 60
  37. 123
  38. 36
  39. 45
  40. 33

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