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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 846 · 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 76°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  2. 2.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 53° and 45°. What is the exterior angle (in degrees)?
  4. 4.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)?
  5. 5.In triangle ABC, angle A = 45° and angle B = 81°. What is angle C (in degrees)?
  6. 6.In triangle ABC, angle A = 86° and angle B = 28°. What is angle C (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  8. 8.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  9. 9.In triangle ABC, angle A = 34° and angle B = 112°. What is angle C (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  12. 12.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  15. 15.In triangle ABC, angle A = 58° and angle B = 99°. What is angle C (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 25° and 47°. What is the exterior angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 3 cm, 3 cm and 11 cm? (a) No (b) Yes
  19. 19.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)?
  20. 20.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  21. 21.The two interior opposite angles of a triangle are 67° and 36°. What is the exterior angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  23. 23.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 70° and angle B = 34°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 22° and 23°. What is the exterior angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  31. 31.In triangle ABC, angle A = 69° and angle B = 31°. What is angle C (in degrees)?
  32. 32.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  33. 33.In triangle ABC, angle A = 33° and angle B = 81°. What is angle C (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 62° and 30°. What is the exterior angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  36. 36.An exterior angle of a triangle is 125°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  37. 37.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?

Answer key

  1. 31
  2. 80
  3. 98
  4. 7
  5. 54
  6. 66
  7. 10
  8. 12
  9. 34
  10. 31
  11. 25
  12. 23
  13. 98
  14. 25
  15. 23
  16. 72
  17. 37
  18. No
  19. 36
  20. 17
  21. 103
  22. 90
  23. 42
  24. 88
  25. 76
  26. 77
  27. 33
  28. 45
  29. 62
  30. 90
  31. 80
  32. 40
  33. 66
  34. 92
  35. 30
  36. 52
  37. 26
  38. 42
  39. 66
  40. 76

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