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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 166 · 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.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)?
  2. 2.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  3. 3.Can a triangle have sides of 9 cm, 8 cm and 11 cm? (a) Yes (b) No
  4. 4.In triangle ABC, angle A = 46° and angle B = 26°. What is angle C (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 73° and angle B = 60°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 68° and angle B = 61°. What is angle C (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  11. 11.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 72° and angle B = 72°. What is angle C (in degrees)?
  14. 14.Can a triangle have sides of 4 cm, 4 cm and 12 cm? (a) Yes (b) No
  15. 15.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  17. 17.Can a triangle have sides of 2 cm, 10 cm and 11 cm? (a) No (b) Yes
  18. 18.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  19. 19.An exterior angle of a triangle is 81°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  22. 22.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 31° and angle B = 50°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 61° and angle B = 92°. What is angle C (in degrees)?
  26. 26.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  27. 27.Can a triangle have sides of 24 cm, 11 cm and 10 cm? (a) Yes (b) No
  28. 28.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 77° and 62°. What is the exterior angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 31° and 48°. What is the exterior angle (in degrees)?
  34. 34.Can a triangle have sides of 9 cm, 2 cm and 9 cm? (a) Yes (b) No
  35. 35.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  37. 37.Can a triangle have sides of 7 cm, 11 cm and 4 cm? (a) Yes (b) No
  38. 38.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 37° and 66°. What is the exterior angle (in degrees)?
  40. 40.Can a triangle have sides of 9 cm, 5 cm and 18 cm? (a) No (b) Yes

Answer key

  1. 15
  2. 36
  3. Yes
  4. 108
  5. 29
  6. 66
  7. 47
  8. 51
  9. 61
  10. 13
  11. 79
  12. 63
  13. 36
  14. No
  15. 122
  16. 17
  17. Yes
  18. 124
  19. 59
  20. 20
  21. 45
  22. 29
  23. 40
  24. 99
  25. 27
  26. 72
  27. No
  28. 54
  29. 46
  30. 14
  31. 139
  32. 72
  33. 79
  34. Yes
  35. 100
  36. 90
  37. No
  38. 22
  39. 103
  40. No

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