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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 473 · 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 29°. What is the third angle (in degrees)?
  2. 2.Can a triangle have sides of 14 cm, 7 cm and 5 cm? (a) Yes (b) No
  3. 3.Can a triangle have sides of 14 cm, 6 cm and 5 cm? (a) No (b) Yes
  4. 4.Can a triangle have sides of 2 cm, 2 cm and 2 cm? (a) Yes (b) No
  5. 5.In triangle ABC, angle A = 94° and angle B = 61°. What is angle C (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 42° and angle B = 42°. What is angle C (in degrees)?
  9. 9.Can a triangle have sides of 12 cm, 25 cm and 10 cm? (a) No (b) Yes
  10. 10.Can a triangle have sides of 10 cm, 23 cm and 11 cm? (a) No (b) Yes
  11. 11.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  12. 12.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  13. 13.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  14. 14.The two interior opposite angles of a triangle are 37° and 60°. What is the exterior angle (in degrees)?
  15. 15.In triangle ABC, angle A = 29° and angle B = 118°. What is angle C (in degrees)?
  16. 16.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)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  18. 18.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  20. 20.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  22. 22.In triangle ABC, angle A = 57° and angle B = 100°. What is angle C (in degrees)?
  23. 23.In triangle ABC, angle A = 31° and angle B = 107°. What is angle C (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 80° and 77°. What is the exterior angle (in degrees)?
  28. 28.In triangle ABC, angle A = 28° and angle B = 47°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 60° and angle B = 34°. What is angle C (in degrees)?
  30. 30.Can a triangle have sides of 2 cm, 12 cm and 7 cm? (a) No (b) Yes
  31. 31.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  32. 32.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)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  34. 34.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 86°. What is each of the other two angles (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 74° and 35°. What is the exterior angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  39. 39.In triangle ABC, angle A = 69° and angle B = 34°. What is angle C (in degrees)?
  40. 40.Can a triangle have sides of 17 cm, 9 cm and 12 cm? (a) Yes (b) No

Answer key

  1. 61
  2. No
  3. No
  4. Yes
  5. 25
  6. 10
  7. 74
  8. 96
  9. No
  10. No
  11. 36
  12. 48
  13. 24
  14. 97
  15. 33
  16. 3
  17. 77
  18. 72
  19. 10
  20. 21
  21. 12
  22. 23
  23. 42
  24. 69
  25. 30
  26. 76
  27. 157
  28. 105
  29. 86
  30. No
  31. 30
  32. 15
  33. 33
  34. 29
  35. 47
  36. 109
  37. 64
  38. 17
  39. 77
  40. Yes

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