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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 830 · 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 3 cm and 4 cm. How long is the longest side (in cm)?
  2. 2.The two interior opposite angles of a triangle are 79° and 74°. What is the exterior angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 21° and angle B = 41°. What is angle C (in degrees)?
  5. 5.Can a triangle have sides of 3 cm, 9 cm and 14 cm? (a) Yes (b) No
  6. 6.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  8. 8.In triangle ABC, angle A = 66° and angle B = 77°. What is angle C (in degrees)?
  9. 9.Can a triangle have sides of 9 cm, 4 cm and 6 cm? (a) No (b) Yes
  10. 10.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  11. 11.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  12. 12.In triangle ABC, angle A = 56° and angle B = 35°. What is angle C (in degrees)?
  13. 13.Can a triangle have sides of 9 cm, 4 cm and 12 cm? (a) No (b) Yes
  14. 14.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 54° and 42°. What is the exterior angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  18. 18.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  19. 19.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  20. 20.In triangle ABC, angle A = 48° and angle B = 40°. What is angle C (in degrees)?
  21. 21.In triangle ABC, angle A = 31° and angle B = 125°. What is angle C (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 50° each. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 21° and angle B = 35°. What is angle C (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 55° and 35°. What is the exterior angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  26. 26.In triangle ABC, angle A = 100° and angle B = 25°. What is angle C (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  28. 28.In triangle ABC, angle A = 83° and angle B = 35°. What is angle C (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  32. 32.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)?
  33. 33.Can a triangle have sides of 7 cm, 8 cm and 8 cm? (a) Yes (b) No
  34. 34.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  38. 38.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  39. 39.Can a triangle have sides of 12 cm, 6 cm and 16 cm? (a) Yes (b) No
  40. 40.In triangle ABC, angle A = 78° and angle B = 29°. What is angle C (in degrees)?

Answer key

  1. 5
  2. 153
  3. 37
  4. 118
  5. No
  6. 40
  7. 40
  8. 37
  9. Yes
  10. 18
  11. 136
  12. 89
  13. Yes
  14. 26
  15. 45
  16. 96
  17. 79
  18. 79
  19. 59
  20. 92
  21. 24
  22. 80
  23. 124
  24. 90
  25. 22
  26. 55
  27. 11
  28. 62
  29. 17
  30. 60
  31. 64
  32. 15
  33. Yes
  34. 84
  35. 80
  36. 46
  37. 20
  38. 66
  39. Yes
  40. 73

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