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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 713 · 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 = 27° and angle B = 93°. What is angle C (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  4. 4.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  6. 6.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (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.In triangle ABC, angle A = 81° and angle B = 23°. What is angle C (in degrees)?
  10. 10.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  11. 11.Can a triangle have sides of 19 cm, 9 cm and 7 cm? (a) Yes (b) No
  12. 12.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  14. 14.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  15. 15.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  16. 16.Can a triangle have sides of 4 cm, 2 cm and 2 cm? (a) No (b) Yes
  17. 17.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  18. 18.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 10 cm, 11 cm and 19 cm? (a) No (b) Yes
  20. 20.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 78° and angle B = 22°. What is angle C (in degrees)?
  24. 24.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)?
  25. 25.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)?
  26. 26.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)?
  27. 27.Can a triangle have sides of 11 cm, 8 cm and 10 cm? (a) No (b) Yes
  28. 28.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  29. 29.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  30. 30.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  31. 31.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  32. 32.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  33. 33.Can a triangle have sides of 8 cm, 6 cm and 15 cm? (a) Yes (b) No
  34. 34.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  35. 35.Can a triangle have sides of 14 cm, 5 cm and 5 cm? (a) No (b) Yes
  36. 36.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 92° and angle B = 34°. What is angle C (in degrees)?

Answer key

  1. 60
  2. 75
  3. 45
  4. 24
  5. 34
  6. 40
  7. 33
  8. 70
  9. 76
  10. 75
  11. No
  12. 63
  13. 90
  14. 9
  15. 80
  16. No
  17. 39
  18. 59
  19. Yes
  20. 53
  21. 74
  22. 65
  23. 80
  24. 8
  25. 15
  26. 7
  27. Yes
  28. 79
  29. 51
  30. 51
  31. 10
  32. 45
  33. No
  34. 48
  35. No
  36. 76
  37. 72
  38. 64
  39. 41
  40. 54

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