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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 861 · 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 = 42° and angle B = 58°. What is angle C (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  3. 3.Can a triangle have sides of 9 cm, 8 cm and 3 cm? (a) No (b) Yes
  4. 4.In triangle ABC, angle A = 78° and angle B = 21°. What is angle C (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  6. 6.In triangle ABC, angle A = 85° and angle B = 42°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 66° and angle B = 63°. What is angle C (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  9. 9.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  12. 12.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  15. 15.Can a triangle have sides of 6 cm, 18 cm and 7 cm? (a) No (b) Yes
  16. 16.In triangle ABC, angle A = 85° and angle B = 62°. What is angle C (in degrees)?
  17. 17.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 19 cm, 6 cm and 12 cm? (a) No (b) Yes
  20. 20.An exterior angle of a triangle is 62°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 29° and 68°. What is the exterior angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 30° and angle B = 95°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  27. 27.An exterior angle of a triangle is 50°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  32. 32.In triangle ABC, angle A = 87° and angle B = 67°. What is angle C (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  34. 34.In triangle ABC, angle A = 53° and angle B = 67°. What is angle C (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 42° and 50°. What is the exterior angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  37. 37.In triangle ABC, angle A = 100° and angle B = 54°. What is angle C (in degrees)?
  38. 38.Can a triangle have sides of 12 cm, 7 cm and 4 cm? (a) No (b) Yes
  39. 39.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  40. 40.Can a triangle have sides of 11 cm, 4 cm and 9 cm? (a) Yes (b) No

Answer key

  1. 80
  2. 17
  3. Yes
  4. 81
  5. 25
  6. 53
  7. 51
  8. 26
  9. 26
  10. 54
  11. 15
  12. 25
  13. 65
  14. 27
  15. No
  16. 33
  17. 62
  18. 63
  19. No
  20. 27
  21. 97
  22. 16
  23. 19
  24. 55
  25. 41
  26. 77
  27. 22
  28. 20
  29. 76
  30. 60
  31. 49
  32. 26
  33. 23
  34. 60
  35. 92
  36. 56
  37. 26
  38. No
  39. 100
  40. Yes

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