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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 867 · 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 an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  2. 2.In triangle ABC, angle A = 79° and angle B = 48°. What is angle C (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 45° and 67°. What is the exterior angle (in degrees)?
  8. 8.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  10. 10.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  12. 12.Can a triangle have sides of 12 cm, 9 cm and 12 cm? (a) Yes (b) No
  13. 13.The two interior opposite angles of a triangle are 44° and 77°. What is the exterior angle (in degrees)?
  14. 14.In triangle ABC, angle A = 48° and angle B = 25°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 64° and angle B = 87°. What is angle C (in degrees)?
  16. 16.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 61° and 53°. What is the exterior angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 29° and 51°. What is the exterior angle (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  21. 21.Can a triangle have sides of 7 cm, 7 cm and 10 cm? (a) Yes (b) No
  22. 22.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 68° and angle B = 32°. What is angle C (in degrees)?
  24. 24.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  28. 28.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  29. 29.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  31. 31.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  33. 33.In triangle ABC, angle A = 92° and angle B = 31°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 9 cm, 8 cm and 7 cm? (a) No (b) Yes
  35. 35.In triangle ABC, angle A = 59° and angle B = 31°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 48° and angle B = 32°. What is angle C (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  38. 38.In an isosceles triangle, the two equal angles are 55° each. What is the third angle (in degrees)?
  39. 39.Can a triangle have sides of 5 cm, 5 cm and 6 cm? (a) Yes (b) No
  40. 40.Can a triangle have sides of 7 cm, 9 cm and 5 cm? (a) No (b) Yes

Answer key

  1. 16
  2. 53
  3. 46
  4. 72
  5. 36
  6. 67
  7. 112
  8. 63
  9. 25
  10. 77
  11. 25
  12. Yes
  13. 121
  14. 107
  15. 29
  16. 67
  17. 63
  18. 114
  19. 80
  20. 26
  21. Yes
  22. 120
  23. 80
  24. 42
  25. 20
  26. 134
  27. 80
  28. 7
  29. 54
  30. 72
  31. 84
  32. 19
  33. 57
  34. Yes
  35. 90
  36. 100
  37. 17
  38. 70
  39. Yes
  40. Yes

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