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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 567 · 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 = 67° and angle B = 26°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  4. 4.Can a triangle have sides of 11 cm, 5 cm and 21 cm? (a) Yes (b) No
  5. 5.Can a triangle have sides of 26 cm, 12 cm and 10 cm? (a) Yes (b) No
  6. 6.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  8. 8.In triangle ABC, angle A = 26° and angle B = 28°. What is angle C (in degrees)?
  9. 9.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)?
  10. 10.Can a triangle have sides of 9 cm, 9 cm and 18 cm? (a) Yes (b) No
  11. 11.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 50° and 32°. What is the exterior angle (in degrees)?
  13. 13.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)?
  14. 14.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  15. 15.In triangle ABC, angle A = 75° and angle B = 37°. What is angle C (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 43° and angle B = 97°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 70° and angle B = 71°. What is angle C (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 98° and angle B = 35°. What is angle C (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 51° and 75°. What is the exterior angle (in degrees)?
  25. 25.An exterior angle of a triangle is 44°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  27. 27.In triangle ABC, angle A = 34° and angle B = 58°. What is angle C (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 31° and 47°. What is the exterior angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 40° and 79°. What is the exterior angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  32. 32.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 85° and angle B = 27°. What is angle C (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  36. 36.The two interior opposite angles of a triangle are 45° and 28°. What is the exterior angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  38. 38.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  39. 39.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  40. 40.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)?

Answer key

  1. 87
  2. 40
  3. 84
  4. No
  5. No
  6. 32
  7. 17
  8. 126
  9. 24
  10. No
  11. 65
  12. 82
  13. 8
  14. 41
  15. 68
  16. 100
  17. 40
  18. 39
  19. 16
  20. 134
  21. 48
  22. 138
  23. 47
  24. 126
  25. 21
  26. 36
  27. 88
  28. 110
  29. 78
  30. 119
  31. 79
  32. 29
  33. 38
  34. 68
  35. 17
  36. 73
  37. 59
  38. 5
  39. 65
  40. 10

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