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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 27 · 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 a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  2. 2.In triangle ABC, angle A = 80° and angle B = 30°. What is angle C (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  4. 4.In triangle ABC, angle A = 42° and angle B = 38°. What is angle C (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  6. 6.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)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 76°. What is each of the other two angles (in degrees)?
  8. 8.In triangle ABC, angle A = 55° and angle B = 73°. What is angle C (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 54° and 35°. What is the exterior angle (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 24° and 37°. What is the exterior angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 49° and 37°. What is the exterior angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 70° and 80°. What is the exterior angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 70° and angle B = 59°. What is angle C (in degrees)?
  18. 18.Can a triangle have sides of 12 cm, 10 cm and 22 cm? (a) Yes (b) No
  19. 19.In triangle ABC, angle A = 21° and angle B = 124°. What is angle C (in degrees)?
  20. 20.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  21. 21.In triangle ABC, angle A = 84° and angle B = 35°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 73° and angle B = 57°. What is angle C (in degrees)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  24. 24.In triangle ABC, angle A = 76° and angle B = 75°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 34° and angle B = 41°. What is angle C (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 30° and 41°. What is the exterior angle (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 28° and 34°. What is the exterior angle (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (in degrees)?
  30. 30.An exterior angle of a triangle is 62°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  33. 33.Can a triangle have sides of 12 cm, 12 cm and 3 cm? (a) No (b) Yes
  34. 34.In triangle ABC, angle A = 76° and angle B = 46°. What is angle C (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  37. 37.In triangle ABC, angle A = 93° and angle B = 55°. What is angle C (in degrees)?
  38. 38.Can a triangle have sides of 9 cm, 7 cm and 7 cm? (a) Yes (b) No
  39. 39.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  40. 40.In triangle ABC, angle A = 82° and angle B = 71°. What is angle C (in degrees)?

Answer key

  1. 63
  2. 70
  3. 90
  4. 100
  5. 27
  6. 10
  7. 52
  8. 52
  9. 75
  10. 89
  11. 61
  12. 76
  13. 86
  14. 150
  15. 20
  16. 52
  17. 51
  18. No
  19. 35
  20. 80
  21. 61
  22. 50
  23. 29
  24. 29
  25. 105
  26. 71
  27. 22
  28. 62
  29. 68
  30. 32
  31. 36
  32. 25
  33. Yes
  34. 58
  35. 14
  36. 41
  37. 32
  38. Yes
  39. 74
  40. 27

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