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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 638 · 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 24°. What is each of the other two angles (in degrees)?
  2. 2.Can a triangle have sides of 8 cm, 5 cm and 5 cm? (a) Yes (b) No
  3. 3.In triangle ABC, angle A = 68° and angle B = 31°. What is angle C (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  5. 5.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)?
  6. 6.In triangle ABC, angle A = 58° and angle B = 42°. What is angle C (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 56° and 26°. What is the exterior angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  12. 12.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  14. 14.Can a triangle have sides of 8 cm, 20 cm and 8 cm? (a) Yes (b) No
  15. 15.Can a triangle have sides of 9 cm, 15 cm and 5 cm? (a) Yes (b) No
  16. 16.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  17. 17.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  18. 18.An exterior angle of a triangle is 53°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  19. 19.In triangle ABC, angle A = 50° and angle B = 37°. What is angle C (in degrees)?
  20. 20.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  21. 21.Can a triangle have sides of 9 cm, 10 cm and 3 cm? (a) No (b) Yes
  22. 22.In triangle ABC, angle A = 67° and angle B = 32°. What is angle C (in degrees)?
  23. 23.In triangle ABC, angle A = 36° and angle B = 28°. What is angle C (in degrees)?
  24. 24.Can a triangle have sides of 12 cm, 22 cm and 9 cm? (a) Yes (b) No
  25. 25.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)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  28. 28.Can a triangle have sides of 2 cm, 14 cm and 9 cm? (a) Yes (b) No
  29. 29.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)?
  30. 30.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  34. 34.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 41° and 36°. What is the exterior angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  37. 37.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  38. 38.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?

Answer key

  1. 78
  2. Yes
  3. 81
  4. 90
  5. 3
  6. 80
  7. 75
  8. 70
  9. 82
  10. 41
  11. 17
  12. 53
  13. 90
  14. No
  15. No
  16. 11
  17. 40
  18. 21
  19. 93
  20. 8
  21. Yes
  22. 81
  23. 116
  24. No
  25. 24
  26. 53
  27. 61
  28. No
  29. 24
  30. 80
  31. 20
  32. 42
  33. 72
  34. 35
  35. 77
  36. 57
  37. 65
  38. 50
  39. 25
  40. 77

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