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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 175 · 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 interior opposite angles of a triangle are 23° and 52°. What is the exterior angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 49° and 27°. What is the exterior angle (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  5. 5.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)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  8. 8.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  9. 9.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 2 cm, 3 cm and 4 cm? (a) Yes (b) No
  12. 12.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 34° and 41°. What is the exterior angle (in degrees)?
  15. 15.In triangle ABC, angle A = 38° and angle B = 72°. What is angle C (in degrees)?
  16. 16.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  17. 17.Can a triangle have sides of 8 cm, 5 cm and 5 cm? (a) No (b) Yes
  18. 18.In triangle ABC, angle A = 33° and angle B = 34°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  20. 20.In triangle ABC, angle A = 95° and angle B = 55°. What is angle C (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles (in degrees)?
  22. 22.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  28. 28.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  29. 29.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  30. 30.Can a triangle have sides of 4 cm, 4 cm and 13 cm? (a) Yes (b) No
  31. 31.Can a triangle have sides of 10 cm, 3 cm and 8 cm? (a) No (b) Yes
  32. 32.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  33. 33.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)?
  34. 34.The two interior opposite angles of a triangle are 27° and 53°. What is the exterior angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 57° and angle B = 36°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  38. 38.In triangle ABC, angle A = 49° and angle B = 40°. What is angle C (in degrees)?
  39. 39.An exterior angle of a triangle is 142°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?

Answer key

  1. 75
  2. 69
  3. 76
  4. 24
  5. 15
  6. 14
  7. 86
  8. 24
  9. 45
  10. 24
  11. Yes
  12. 52
  13. 19
  14. 75
  15. 70
  16. 58
  17. Yes
  18. 113
  19. 20
  20. 30
  21. 30
  22. 26
  23. 40
  24. 68
  25. 67
  26. 30
  27. 5
  28. 22
  29. 54
  30. No
  31. Yes
  32. 90
  33. 7
  34. 80
  35. 47
  36. 87
  37. 72
  38. 91
  39. 67
  40. 13

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