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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 872 · 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 = 65° and angle B = 48°. What is angle C (in degrees)?
  2. 2.In triangle ABC, angle A = 28° and angle B = 81°. What is angle C (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  5. 5.In triangle ABC, angle A = 56° and angle B = 90°. What is angle C (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  7. 7.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 30° and angle B = 30°. What is angle C (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 36° and 46°. What is the exterior angle (in degrees)?
  12. 12.Can a triangle have sides of 20 cm, 9 cm and 10 cm? (a) No (b) Yes
  13. 13.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  16. 16.In triangle ABC, angle A = 48° and angle B = 27°. What is angle C (in degrees)?
  17. 17.Can a triangle have sides of 8 cm, 11 cm and 6 cm? (a) Yes (b) No
  18. 18.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  19. 19.In triangle ABC, angle A = 62° and angle B = 70°. What is angle C (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 64° and angle B = 60°. What is angle C (in degrees)?
  22. 22.Can a triangle have sides of 10 cm, 11 cm and 11 cm? (a) No (b) Yes
  23. 23.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 4 cm, 9 cm and 2 cm? (a) Yes (b) No
  25. 25.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  26. 26.In triangle ABC, angle A = 20° and angle B = 23°. What is angle C (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 64° and 75°. What is the exterior angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  31. 31.In triangle ABC, angle A = 71° and angle B = 82°. What is angle C (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  34. 34.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  35. 35.In triangle ABC, angle A = 96° and angle B = 49°. What is angle C (in degrees)?
  36. 36.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 4 cm, 1 cm and 4 cm? (a) No (b) Yes
  39. 39.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  40. 40.Can a triangle have sides of 9 cm, 3 cm and 2 cm? (a) No (b) Yes

Answer key

  1. 67
  2. 71
  3. 45
  4. 80
  5. 34
  6. 56
  7. 51
  8. 23
  9. 18
  10. 120
  11. 82
  12. No
  13. 13
  14. 39
  15. 16
  16. 105
  17. Yes
  18. 90
  19. 48
  20. 45
  21. 56
  22. Yes
  23. 27
  24. No
  25. 6
  26. 137
  27. 139
  28. 18
  29. 46
  30. 14
  31. 27
  32. 38
  33. 65
  34. 46
  35. 35
  36. 36
  37. 31
  38. Yes
  39. 49
  40. No

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