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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 179 · 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.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  2. 2.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  3. 3.Can a triangle have sides of 4 cm, 5 cm and 8 cm? (a) Yes (b) No
  4. 4.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  5. 5.In triangle ABC, angle A = 66° and angle B = 27°. What is angle C (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (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.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  9. 9.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  10. 10.In triangle ABC, angle A = 99° and angle B = 24°. 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.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  13. 13.In triangle ABC, angle A = 56° and angle B = 68°. What is angle C (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 76° and 28°. What is the exterior angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  16. 16.An exterior angle of a triangle is 141°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  18. 18.The two interior opposite angles of a triangle are 54° and 48°. What is the exterior angle (in degrees)?
  19. 19.In triangle ABC, angle A = 87° and angle B = 29°. What is angle C (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 37° and 27°. What is the exterior angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 6 cm, 12 cm and 9 cm? (a) No (b) Yes
  25. 25.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  26. 26.In triangle ABC, angle A = 84° and angle B = 29°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 46° and angle B = 52°. What is angle C (in degrees)?
  28. 28.In triangle ABC, angle A = 33° and angle B = 66°. What is angle C (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  30. 30.In triangle ABC, angle A = 25° and angle B = 117°. What is angle C (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 64° and 58°. What is the exterior angle (in degrees)?
  32. 32.In triangle ABC, angle A = 90° and angle B = 23°. What is angle C (in degrees)?
  33. 33.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  35. 35.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  37. 37.In triangle ABC, angle A = 78° and angle B = 34°. What is angle C (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  40. 40.The two interior opposite angles of a triangle are 40° and 48°. What is the exterior angle (in degrees)?

Answer key

  1. 25
  2. 84
  3. Yes
  4. 26
  5. 87
  6. 108
  7. 24
  8. 36
  9. 15
  10. 57
  11. 69
  12. 18
  13. 56
  14. 104
  15. 22
  16. 80
  17. 39
  18. 102
  19. 64
  20. 20
  21. 39
  22. 64
  23. 77
  24. Yes
  25. 76
  26. 67
  27. 82
  28. 81
  29. 25
  30. 38
  31. 122
  32. 67
  33. 68
  34. 10
  35. 72
  36. 58
  37. 68
  38. 74
  39. 17
  40. 88

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