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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 882 · 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 triangle ABC, angle A = 59° and angle B = 30°. What is angle C (in degrees)?
  2. 2.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)?
  3. 3.Can a triangle have sides of 26 cm, 11 cm and 10 cm? (a) No (b) Yes
  4. 4.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  6. 6.In triangle ABC, angle A = 68° and angle B = 75°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 37° and angle B = 111°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 86° and angle B = 71°. What is angle C (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 56° and 48°. What is the exterior angle (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  14. 14.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  15. 15.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  16. 16.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  18. 18.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 154°. What is each of the other two angles (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  24. 24.In triangle ABC, angle A = 50° and angle B = 94°. What is angle C (in degrees)?
  25. 25.Can a triangle have sides of 9 cm, 3 cm and 10 cm? (a) Yes (b) No
  26. 26.In triangle ABC, angle A = 76° and angle B = 29°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 3 cm, 9 cm and 8 cm? (a) Yes (b) No
  28. 28.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  30. 30.Can a triangle have sides of 20 cm, 6 cm and 9 cm? (a) No (b) Yes
  31. 31.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  33. 33.In triangle ABC, angle A = 74° and angle B = 82°. What is angle C (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  36. 36.Can a triangle have sides of 17 cm, 2 cm and 11 cm? (a) Yes (b) No
  37. 37.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  38. 38.In triangle ABC, angle A = 58° and angle B = 60°. What is angle C (in degrees)?
  39. 39.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?

Answer key

  1. 91
  2. 24
  3. No
  4. 72
  5. 80
  6. 37
  7. 32
  8. 23
  9. 36
  10. 90
  11. 104
  12. 77
  13. 39
  14. 100
  15. 15
  16. 77
  17. 78
  18. 36
  19. 72
  20. 13
  21. 46
  22. 90
  23. 66
  24. 36
  25. Yes
  26. 75
  27. Yes
  28. 104
  29. 48
  30. No
  31. 28
  32. 74
  33. 24
  34. 69
  35. 54
  36. No
  37. 66
  38. 62
  39. 20
  40. 71

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