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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 701 · 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.Can a triangle have sides of 7 cm, 3 cm and 13 cm? (a) No (b) Yes
  2. 2.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  3. 3.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  4. 4.Can a triangle have sides of 21 cm, 9 cm and 12 cm? (a) Yes (b) No
  5. 5.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 35° and angle B = 82°. What is angle C (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 75° and 80°. What is the exterior angle (in degrees)?
  13. 13.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  14. 14.In triangle ABC, angle A = 33° and angle B = 29°. What is angle C (in degrees)?
  15. 15.An exterior angle of a triangle is 146°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  16. 16.In triangle ABC, angle A = 66° and angle B = 72°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 85° and angle B = 73°. What is angle C (in degrees)?
  18. 18.Can a triangle have sides of 8 cm, 10 cm and 18 cm? (a) Yes (b) No
  19. 19.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  20. 20.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 79° and 49°. What is the exterior angle (in degrees)?
  22. 22.Can a triangle have sides of 9 cm, 6 cm and 12 cm? (a) No (b) Yes
  23. 23.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  26. 26.An exterior angle of a triangle is 139°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  27. 27.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  28. 28.Can a triangle have sides of 7 cm, 3 cm and 6 cm? (a) Yes (b) No
  29. 29.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  30. 30.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 80° and angle B = 61°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 30° and angle B = 84°. What is angle C (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 24° and 54°. What is the exterior angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 36° and 33°. What is the exterior angle (in degrees)?
  35. 35.Can a triangle have sides of 9 cm, 11 cm and 4 cm? (a) No (b) Yes
  36. 36.The two interior opposite angles of a triangle are 47° and 67°. What is the exterior angle (in degrees)?
  37. 37.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)?
  38. 38.The two interior opposite angles of a triangle are 51° and 58°. What is the exterior angle (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?

Answer key

  1. No
  2. 66
  3. 8
  4. No
  5. 20
  6. 76
  7. 36
  8. 24
  9. 67
  10. 74
  11. 63
  12. 155
  13. 27
  14. 118
  15. 66
  16. 42
  17. 22
  18. No
  19. 12
  20. 90
  21. 128
  22. Yes
  23. 19
  24. 33
  25. 29
  26. 67
  27. 5
  28. Yes
  29. 4
  30. 65
  31. 39
  32. 66
  33. 78
  34. 69
  35. Yes
  36. 114
  37. 12
  38. 109
  39. 110
  40. 54

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