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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 810 · 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 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  2. 2.In triangle ABC, angle A = 42° and angle B = 32°. What is angle C (in degrees)?
  3. 3.In triangle ABC, angle A = 23° and angle B = 75°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  5. 5.An exterior angle of a triangle is 48°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 67° and angle B = 20°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  9. 9.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)?
  10. 10.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  12. 12.In triangle ABC, angle A = 72° and angle B = 28°. What is angle C (in degrees)?
  13. 13.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  14. 14.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  15. 15.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  17. 17.Can a triangle have sides of 6 cm, 5 cm and 13 cm? (a) Yes (b) No
  18. 18.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  19. 19.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  20. 20.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 6 cm, 18 cm and 9 cm? (a) Yes (b) No
  23. 23.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  24. 24.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)?
  25. 25.The two interior opposite angles of a triangle are 26° and 42°. What is the exterior angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 30° and 35°. What is the exterior angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 31° and angle B = 81°. What is angle C (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 33° and 55°. What is the exterior angle (in degrees)?
  31. 31.In triangle ABC, angle A = 100° and angle B = 29°. What is angle C (in degrees)?
  32. 32.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  34. 34.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  35. 35.In triangle ABC, angle A = 64° and angle B = 24°. What is angle C (in degrees)?
  36. 36.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  37. 37.An exterior angle of a triangle is 140°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  38. 38.Can a triangle have sides of 7 cm, 2 cm and 8 cm? (a) Yes (b) No
  39. 39.In triangle ABC, angle A = 30° and angle B = 77°. What is angle C (in degrees)?
  40. 40.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?

Answer key

  1. 24
  2. 106
  3. 82
  4. 54
  5. 21
  6. 28
  7. 93
  8. 50
  9. 3
  10. 36
  11. 54
  12. 80
  13. 12
  14. 36
  15. 66
  16. 26
  17. No
  18. 13
  19. 17
  20. 48
  21. 77
  22. No
  23. 120
  24. 7
  25. 68
  26. 62
  27. 65
  28. 65
  29. 68
  30. 88
  31. 51
  32. 100
  33. 40
  34. 38
  35. 92
  36. 79
  37. 77
  38. Yes
  39. 73
  40. 27

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