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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 718 · 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 angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  3. 3.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  4. 4.In triangle ABC, angle A = 25° and angle B = 96°. What is angle C (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 73° and 21°. What is the exterior angle (in degrees)?
  9. 9.An exterior angle of a triangle is 53°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 5 cm, 10 cm and 8 cm? (a) Yes (b) No
  12. 12.In triangle ABC, angle A = 40° and angle B = 100°. What is angle C (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 54° and 80°. What is the exterior angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  15. 15.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)?
  16. 16.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 27° and 24°. What is the exterior angle (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 54° and 70°. What is the exterior angle (in degrees)?
  19. 19.An exterior angle of a triangle is 53°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  20. 20.In triangle ABC, angle A = 69° and angle B = 51°. What is angle C (in degrees)?
  21. 21.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  22. 22.In triangle ABC, angle A = 44° and angle B = 44°. What is angle C (in degrees)?
  23. 23.Can a triangle have sides of 6 cm, 6 cm and 12 cm? (a) No (b) Yes
  24. 24.In triangle ABC, angle A = 95° and angle B = 56°. What is angle C (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 71° and angle B = 38°. What is angle C (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  28. 28.In triangle ABC, angle A = 75° and angle B = 43°. What is angle C (in degrees)?
  29. 29.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)?
  30. 30.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  31. 31.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  32. 32.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  33. 33.In triangle ABC, angle A = 97° and angle B = 48°. What is angle C (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  35. 35.In triangle ABC, angle A = 29° and angle B = 120°. What is angle C (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 33° and 44°. What is the exterior angle (in degrees)?
  37. 37.In triangle ABC, angle A = 89° and angle B = 26°. What is angle C (in degrees)?
  38. 38.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  39. 39.An exterior angle of a triangle is 144°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  40. 40.Can a triangle have sides of 9 cm, 20 cm and 9 cm? (a) No (b) Yes

Answer key

  1. 36
  2. 100
  3. 29
  4. 59
  5. 24
  6. 22
  7. 90
  8. 94
  9. 27
  10. 40
  11. Yes
  12. 40
  13. 134
  14. 18
  15. 7
  16. 132
  17. 51
  18. 124
  19. 20
  20. 60
  21. 100
  22. 92
  23. No
  24. 29
  25. 24
  26. 71
  27. 61
  28. 62
  29. 10
  30. 25
  31. 62
  32. 30
  33. 35
  34. 78
  35. 31
  36. 77
  37. 65
  38. 9
  39. 79
  40. No

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