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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 354 · 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 an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?
  2. 2.In triangle ABC, angle A = 31° and angle B = 116°. What is angle C (in degrees)?
  3. 3.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  4. 4.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  5. 5.Can a triangle have sides of 12 cm, 11 cm and 3 cm? (a) No (b) Yes
  6. 6.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  7. 7.In triangle ABC, angle A = 50° and angle B = 31°. What is angle C (in degrees)?
  8. 8.An exterior angle of a triangle is 157°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  9. 9.In triangle ABC, angle A = 91° and angle B = 63°. What is angle C (in degrees)?
  10. 10.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  12. 12.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)?
  13. 13.Can a triangle have sides of 6 cm, 7 cm and 9 cm? (a) No (b) Yes
  14. 14.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)?
  15. 15.In triangle ABC, angle A = 78° and angle B = 26°. What is angle C (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  17. 17.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  19. 19.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  20. 20.Can a triangle have sides of 11 cm, 2 cm and 12 cm? (a) No (b) Yes
  21. 21.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 67° and 73°. What is the exterior angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  25. 25.Can a triangle have sides of 10 cm, 23 cm and 10 cm? (a) Yes (b) No
  26. 26.In triangle ABC, angle A = 86° and angle B = 68°. What is angle C (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 33° and 31°. What is the exterior angle (in degrees)?
  28. 28.Can a triangle have sides of 22 cm, 6 cm and 12 cm? (a) Yes (b) No
  29. 29.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 30° and angle B = 24°. What is angle C (in degrees)?
  31. 31.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  32. 32.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  33. 33.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  34. 34.In triangle ABC, angle A = 94° and angle B = 21°. What is angle C (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 27° and angle B = 121°. What is angle C (in degrees)?
  37. 37.In triangle ABC, angle A = 83° and angle B = 63°. What is angle C (in degrees)?
  38. 38.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?

Answer key

  1. 38
  2. 33
  3. 36
  4. 18
  5. Yes
  6. 90
  7. 99
  8. 80
  9. 26
  10. 40
  11. 41
  12. 36
  13. Yes
  14. 24
  15. 76
  16. 13
  17. 28
  18. 17
  19. 70
  20. Yes
  21. 69
  22. 52
  23. 140
  24. 54
  25. No
  26. 26
  27. 64
  28. No
  29. 138
  30. 126
  31. 49
  32. 6
  33. 3
  34. 65
  35. 29
  36. 32
  37. 34
  38. 75
  39. 20
  40. 77

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