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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 295 · 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 47° each. What is the third angle (in degrees)?
  2. 2.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 10 cm, 9 cm and 21 cm? (a) Yes (b) No
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 21° and 21°. What is the exterior angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  9. 9.Can a triangle have sides of 22 cm, 12 cm and 5 cm? (a) Yes (b) No
  10. 10.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  11. 11.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  12. 12.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  13. 13.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  15. 15.An exterior angle of a triangle is 140°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  17. 17.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  18. 18.In triangle ABC, angle A = 67° and angle B = 61°. What is angle C (in degrees)?
  19. 19.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  20. 20.Can a triangle have sides of 4 cm, 8 cm and 11 cm? (a) No (b) Yes
  21. 21.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  22. 22.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 36° and 27°. What is the exterior angle (in degrees)?
  24. 24.In triangle ABC, angle A = 48° and angle B = 53°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 54° each. What is the third angle (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 38° and 33°. What is the exterior angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 67° and 76°. What is the exterior angle (in degrees)?
  30. 30.In triangle ABC, angle A = 86° and angle B = 66°. What is angle C (in degrees)?
  31. 31.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  32. 32.In triangle ABC, angle A = 50° and angle B = 61°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 31° and angle B = 106°. What is angle C (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  35. 35.In triangle ABC, angle A = 79° and angle B = 65°. What is angle C (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  38. 38.In triangle ABC, angle A = 23° and angle B = 122°. What is angle C (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  40. 40.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?

Answer key

  1. 86
  2. 45
  3. 74
  4. No
  5. 20
  6. 30
  7. 42
  8. 17
  9. No
  10. 15
  11. 39
  12. 25
  13. 15
  14. 120
  15. 79
  16. 62
  17. 76
  18. 52
  19. 69
  20. Yes
  21. 17
  22. 35
  23. 63
  24. 79
  25. 72
  26. 71
  27. 24
  28. 16
  29. 143
  30. 28
  31. 65
  32. 69
  33. 43
  34. 80
  35. 36
  36. 47
  37. 25
  38. 35
  39. 32
  40. 15

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