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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 264 · 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 = 22° and angle B = 123°. What is angle C (in degrees)?
  2. 2.Can a triangle have sides of 5 cm, 4 cm and 5 cm? (a) Yes (b) No
  3. 3.In triangle ABC, angle A = 37° and angle B = 96°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 86° and angle B = 55°. What is angle C (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.Can a triangle have sides of 10 cm, 5 cm and 10 cm? (a) Yes (b) No
  9. 9.In triangle ABC, angle A = 53° and angle B = 89°. What is angle C (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  12. 12.Can a triangle have sides of 20 cm, 9 cm and 7 cm? (a) Yes (b) No
  13. 13.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  15. 15.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)?
  16. 16.In triangle ABC, angle A = 48° and angle B = 103°. What is angle C (in degrees)?
  17. 17.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  18. 18.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 21° and 75°. What is the exterior angle (in degrees)?
  20. 20.In triangle ABC, angle A = 20° and angle B = 34°. What is angle C (in degrees)?
  21. 21.In triangle ABC, angle A = 94° and angle B = 45°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 50° and angle B = 91°. What is angle C (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  27. 27.In triangle ABC, angle A = 89° and angle B = 65°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 11 cm, 11 cm and 2 cm? (a) Yes (b) No
  29. 29.Can a triangle have sides of 11 cm, 8 cm and 13 cm? (a) No (b) Yes
  30. 30.In triangle ABC, angle A = 26° and angle B = 64°. What is angle C (in degrees)?
  31. 31.An exterior angle of a triangle is 63°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  33. 33.In triangle ABC, angle A = 66° and angle B = 64°. What is angle C (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 79° and 67°. What is the exterior angle (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  37. 37.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  39. 39.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?

Answer key

  1. 35
  2. Yes
  3. 47
  4. 120
  5. 70
  6. 39
  7. 33
  8. Yes
  9. 38
  10. 63
  11. 100
  12. No
  13. 55
  14. 20
  15. 7
  16. 29
  17. 51
  18. 47
  19. 96
  20. 126
  21. 41
  22. 39
  23. 90
  24. 72
  25. 45
  26. 17
  27. 26
  28. Yes
  29. Yes
  30. 90
  31. 41
  32. 46
  33. 50
  34. 37
  35. 146
  36. 5
  37. 41
  38. 67
  39. 90
  40. 67

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