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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 204 · 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.

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  1. 1.In triangle ABC, angle A = 82° and angle B = 23°. What is angle C (in degrees)?
  2. 2.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)?
  3. 3.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 32° and 27°. What is the exterior angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 154°. What is each of the other two angles (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  9. 9.Can a triangle have sides of 5 cm, 4 cm and 12 cm? (a) No (b) Yes
  10. 10.In triangle ABC, angle A = 56° and angle B = 81°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 38° and angle B = 77°. What is angle C (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  13. 13.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  15. 15.Can a triangle have sides of 10 cm, 3 cm and 13 cm? (a) Yes (b) No
  16. 16.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 33° and angle B = 114°. What is angle C (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  19. 19.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  22. 22.Can a triangle have sides of 6 cm, 6 cm and 5 cm? (a) Yes (b) No
  23. 23.Can a triangle have sides of 7 cm, 12 cm and 10 cm? (a) Yes (b) No
  24. 24.Can a triangle have sides of 9 cm, 11 cm and 24 cm? (a) No (b) Yes
  25. 25.The two interior opposite angles of a triangle are 23° and 49°. What is the exterior angle (in degrees)?
  26. 26.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)?
  27. 27.Can a triangle have sides of 7 cm, 4 cm and 14 cm? (a) Yes (b) No
  28. 28.The two interior opposite angles of a triangle are 51° and 53°. What is the exterior angle (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  30. 30.Can a triangle have sides of 6 cm, 8 cm and 10 cm? (a) Yes (b) No
  31. 31.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  33. 33.Can a triangle have sides of 10 cm, 10 cm and 20 cm? (a) Yes (b) No
  34. 34.Can a triangle have sides of 9 cm, 10 cm and 9 cm? (a) Yes (b) No
  35. 35.In triangle ABC, angle A = 85° and angle B = 56°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 32° and angle B = 68°. What is angle C (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 52° and 32°. What is the exterior angle (in degrees)?
  38. 38.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  39. 39.In triangle ABC, angle A = 50° and angle B = 77°. What is angle C (in degrees)?
  40. 40.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?

Answer key

  1. 75
  2. 9
  3. 60
  4. 59
  5. 37
  6. 16
  7. 13
  8. 26
  9. No
  10. 43
  11. 65
  12. 17
  13. 80
  14. 90
  15. No
  16. 23
  17. 33
  18. 20
  19. 88
  20. 70
  21. 45
  22. Yes
  23. Yes
  24. No
  25. 72
  26. 15
  27. No
  28. 104
  29. 44
  30. Yes
  31. 90
  32. 90
  33. No
  34. Yes
  35. 39
  36. 80
  37. 84
  38. 8
  39. 53
  40. 120

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