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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 988 · 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 15 cm and 8 cm. How long is the longest side (in cm)?
  2. 2.The two interior opposite angles of a triangle are 49° and 68°. What is the exterior angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  4. 4.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  5. 5.In triangle ABC, angle A = 23° and angle B = 35°. What is angle C (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 154°. What is each of the other two angles (in degrees)?
  7. 7.Can a triangle have sides of 9 cm, 7 cm and 4 cm? (a) No (b) Yes
  8. 8.In an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 61° and 43°. What is the exterior angle (in degrees)?
  10. 10.In triangle ABC, angle A = 72° and angle B = 48°. What is angle C (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 41° and angle B = 57°. What is angle C (in degrees)?
  14. 14.Can a triangle have sides of 5 cm, 11 cm and 11 cm? (a) Yes (b) No
  15. 15.Can a triangle have sides of 2 cm, 5 cm and 6 cm? (a) Yes (b) No
  16. 16.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  17. 17.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  19. 19.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 72° and 59°. What is the exterior angle (in degrees)?
  21. 21.In triangle ABC, angle A = 83° and angle B = 37°. What is angle C (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  24. 24.Can a triangle have sides of 2 cm, 9 cm and 12 cm? (a) Yes (b) No
  25. 25.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  26. 26.Can a triangle have sides of 2 cm, 7 cm and 7 cm? (a) No (b) Yes
  27. 27.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 87° and angle B = 39°. What is angle C (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  31. 31.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 76° each. What is the third angle (in degrees)?
  36. 36.Can a triangle have sides of 3 cm, 7 cm and 3 cm? (a) Yes (b) No
  37. 37.In an isosceles triangle, the angle between the two equal sides is 94°. What is each of the other two angles (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  39. 39.In triangle ABC, angle A = 65° and angle B = 45°. What is angle C (in degrees)?
  40. 40.In triangle ABC, angle A = 88° and angle B = 63°. What is angle C (in degrees)?

Answer key

  1. 17
  2. 117
  3. 15
  4. 8
  5. 122
  6. 13
  7. Yes
  8. 54
  9. 104
  10. 60
  11. 18
  12. 50
  13. 82
  14. Yes
  15. Yes
  16. 77
  17. 54
  18. 25
  19. 68
  20. 131
  21. 60
  22. 64
  23. 39
  24. No
  25. 20
  26. Yes
  27. 30
  28. 79
  29. 54
  30. 31
  31. 33
  32. 59
  33. 90
  34. 57
  35. 28
  36. No
  37. 43
  38. 25
  39. 70
  40. 29

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