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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 871 · 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 angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  4. 4.In triangle ABC, angle A = 95° and angle B = 21°. What is angle C (in degrees)?
  5. 5.Can a triangle have sides of 5 cm, 15 cm and 9 cm? (a) No (b) Yes
  6. 6.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  8. 8.Can a triangle have sides of 4 cm, 10 cm and 12 cm? (a) Yes (b) No
  9. 9.In an isosceles triangle, the angle between the two equal sides is 158°. What is each of the other two angles (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  12. 12.In triangle ABC, angle A = 37° and angle B = 26°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  16. 16.Can a triangle have sides of 4 cm, 17 cm and 11 cm? (a) Yes (b) No
  17. 17.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)?
  18. 18.In triangle ABC, angle A = 31° and angle B = 52°. What is angle C (in degrees)?
  19. 19.Can a triangle have sides of 18 cm, 4 cm and 10 cm? (a) Yes (b) No
  20. 20.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  21. 21.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  22. 22.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 41° and angle B = 48°. What is angle C (in degrees)?
  24. 24.Can a triangle have sides of 5 cm, 6 cm and 7 cm? (a) Yes (b) No
  25. 25.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  26. 26.In triangle ABC, angle A = 52° and angle B = 90°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 27° and angle B = 50°. What is angle C (in degrees)?
  28. 28.In triangle ABC, angle A = 81° and angle B = 44°. What is angle C (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  30. 30.Can a triangle have sides of 7 cm, 9 cm and 16 cm? (a) Yes (b) No
  31. 31.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 47° and 43°. What is the exterior angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 61° and 70°. What is the exterior angle (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  36. 36.In triangle ABC, angle A = 57° and angle B = 78°. What is angle C (in degrees)?
  37. 37.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)?
  38. 38.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?

Answer key

  1. 18
  2. 98
  3. 56
  4. 64
  5. No
  6. 30
  7. 44
  8. Yes
  9. 11
  10. 74
  11. 80
  12. 117
  13. 63
  14. 40
  15. 13
  16. No
  17. 15
  18. 97
  19. No
  20. 13
  21. 17
  22. 126
  23. 91
  24. Yes
  25. 29
  26. 38
  27. 103
  28. 55
  29. 71
  30. No
  31. 23
  32. 90
  33. 36
  34. 131
  35. 37
  36. 45
  37. 24
  38. 49
  39. 36
  40. 19

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