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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 234 · 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 48°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  2. 2.In triangle ABC, angle A = 76° and angle B = 34°. What is angle C (in degrees)?
  3. 3.Can a triangle have sides of 8 cm, 9 cm and 3 cm? (a) Yes (b) No
  4. 4.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  5. 5.In triangle ABC, angle A = 58° and angle B = 52°. What is angle C (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  7. 7.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  10. 10.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)?
  11. 11.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  12. 12.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  14. 14.Can a triangle have sides of 3 cm, 19 cm and 12 cm? (a) No (b) Yes
  15. 15.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 39° and 45°. What is the exterior angle (in degrees)?
  17. 17.In triangle ABC, angle A = 83° and angle B = 28°. What is angle C (in degrees)?
  18. 18.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  19. 19.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  20. 20.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  21. 21.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 40° and angle B = 116°. What is angle C (in degrees)?
  25. 25.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  26. 26.In triangle ABC, angle A = 20° and angle B = 24°. What is angle C (in degrees)?
  27. 27.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  28. 28.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 38° and 55°. What is the exterior angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  31. 31.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  32. 32.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 24° and angle B = 83°. What is angle C (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  36. 36.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)?
  37. 37.An exterior angle of a triangle is 53°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  38. 38.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)?
  39. 39.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?

Answer key

  1. 26
  2. 70
  3. Yes
  4. 41
  5. 70
  6. 102
  7. 44
  8. 14
  9. 14
  10. 20
  11. 33
  12. 46
  13. 5
  14. No
  15. 72
  16. 84
  17. 69
  18. 8
  19. 26
  20. 10
  21. 57
  22. 45
  23. 126
  24. 24
  25. 80
  26. 136
  27. 40
  28. 75
  29. 93
  30. 79
  31. 4
  32. 90
  33. 82
  34. 73
  35. 42
  36. 24
  37. 28
  38. 36
  39. 20
  40. 63

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