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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 331 · 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 a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  3. 3.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 45° and angle B = 97°. What is angle C (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  7. 7.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  8. 8.Can a triangle have sides of 3 cm, 6 cm and 2 cm? (a) No (b) Yes
  9. 9.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)?
  10. 10.Can a triangle have sides of 13 cm, 10 cm and 4 cm? (a) Yes (b) No
  11. 11.In triangle ABC, angle A = 79° and angle B = 66°. What is angle C (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  15. 15.Can a triangle have sides of 8 cm, 2 cm and 8 cm? (a) No (b) Yes
  16. 16.In triangle ABC, angle A = 63° and angle B = 29°. What is angle C (in degrees)?
  17. 17.Can a triangle have sides of 4 cm, 2 cm and 3 cm? (a) No (b) Yes
  18. 18.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  19. 19.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  22. 22.Can a triangle have sides of 10 cm, 9 cm and 20 cm? (a) Yes (b) No
  23. 23.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  25. 25.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  28. 28.In triangle ABC, angle A = 31° and angle B = 120°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 54° and angle B = 76°. What is angle C (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 65° and 27°. What is the exterior angle (in degrees)?
  32. 32.Can a triangle have sides of 7 cm, 11 cm and 16 cm? (a) No (b) Yes
  33. 33.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 27° and angle B = 53°. What is angle C (in degrees)?
  35. 35.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  38. 38.In triangle ABC, angle A = 50° and angle B = 85°. What is angle C (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 30° and 62°. What is the exterior angle (in degrees)?

Answer key

  1. 42
  2. 10
  3. 12
  4. 38
  5. 108
  6. 20
  7. 60
  8. No
  9. 36
  10. Yes
  11. 35
  12. 71
  13. 28
  14. 17
  15. Yes
  16. 88
  17. Yes
  18. 72
  19. 12
  20. 24
  21. 77
  22. No
  23. 64
  24. 20
  25. 90
  26. 29
  27. 20
  28. 29
  29. 50
  30. 69
  31. 92
  32. Yes
  33. 60
  34. 100
  35. 68
  36. 44
  37. 11
  38. 45
  39. 37
  40. 92

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