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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 260 · 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 triangle ABC, angle A = 100° and angle B = 29°. What is angle C (in degrees)?
  2. 2.Can a triangle have sides of 5 cm, 11 cm and 10 cm? (a) No (b) Yes
  3. 3.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  6. 6.Can a triangle have sides of 18 cm, 12 cm and 4 cm? (a) No (b) Yes
  7. 7.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 88° and angle B = 43°. What is angle C (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 49° and 47°. What is the exterior angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  12. 12.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  13. 13.In triangle ABC, angle A = 48° and angle B = 80°. What is angle C (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  15. 15.In triangle ABC, angle A = 87° and angle B = 66°. What is angle C (in degrees)?
  16. 16.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?
  18. 18.In triangle ABC, angle A = 97° and angle B = 44°. What is angle C (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 22 cm, 8 cm and 9 cm? (a) No (b) Yes
  25. 25.In triangle ABC, angle A = 21° and angle B = 136°. What is angle C (in degrees)?
  26. 26.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  27. 27.The two interior opposite angles of a triangle are 33° and 27°. What is the exterior angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 10 cm, 23 cm and 8 cm? (a) Yes (b) No
  32. 32.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles (in degrees)?
  34. 34.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  35. 35.Can a triangle have sides of 2 cm, 10 cm and 9 cm? (a) Yes (b) No
  36. 36.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  37. 37.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  38. 38.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  39. 39.Can a triangle have sides of 9 cm, 4 cm and 9 cm? (a) Yes (b) No
  40. 40.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?

Answer key

  1. 51
  2. Yes
  3. 84
  4. 65
  5. 40
  6. No
  7. 122
  8. 63
  9. 49
  10. 96
  11. 72
  12. 16
  13. 52
  14. 14
  15. 27
  16. 71
  17. 76
  18. 39
  19. 46
  20. 29
  21. 75
  22. 40
  23. 71
  24. No
  25. 23
  26. 12
  27. 60
  28. 67
  29. 56
  30. 128
  31. No
  32. 29
  33. 30
  34. 9
  35. Yes
  36. 30
  37. 5
  38. 25
  39. Yes
  40. 47

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