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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 206 · 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 = 22° and angle B = 99°. What is angle C (in degrees)?
  2. 2.In triangle ABC, angle A = 28° and angle B = 83°. What is angle C (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  4. 4.In triangle ABC, angle A = 30° and angle B = 113°. What is angle C (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 79° and angle B = 25°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 38° and angle B = 84°. What is angle C (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  9. 9.Can a triangle have sides of 2 cm, 9 cm and 4 cm? (a) No (b) Yes
  10. 10.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 10 cm, 6 cm and 4 cm? (a) Yes (b) No
  12. 12.Can a triangle have sides of 6 cm, 5 cm and 16 cm? (a) Yes (b) No
  13. 13.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  16. 16.Can a triangle have sides of 9 cm, 12 cm and 11 cm? (a) No (b) Yes
  17. 17.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  18. 18.An exterior angle of a triangle is 65°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  19. 19.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  21. 21.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  22. 22.An exterior angle of a triangle is 52°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  23. 23.In triangle ABC, angle A = 21° and angle B = 32°. What is angle C (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  25. 25.Can a triangle have sides of 3 cm, 7 cm and 4 cm? (a) Yes (b) No
  26. 26.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  27. 27.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  28. 28.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)?
  29. 29.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  31. 31.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)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 44° and 80°. What is the exterior angle (in degrees)?
  34. 34.In triangle ABC, angle A = 89° and angle B = 29°. What is angle C (in degrees)?
  35. 35.Can a triangle have sides of 2 cm, 4 cm and 3 cm? (a) No (b) Yes
  36. 36.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 41° and angle B = 43°. What is angle C (in degrees)?
  39. 39.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?

Answer key

  1. 59
  2. 69
  3. 17
  4. 37
  5. 76
  6. 76
  7. 58
  8. 88
  9. No
  10. 20
  11. No
  12. No
  13. 36
  14. 62
  15. 25
  16. Yes
  17. 7
  18. 40
  19. 36
  20. 51
  21. 36
  22. 29
  23. 127
  24. 20
  25. No
  26. 31
  27. 21
  28. 3
  29. 73
  30. 68
  31. 24
  32. 70
  33. 124
  34. 62
  35. Yes
  36. 42
  37. 90
  38. 96
  39. 45
  40. 47

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