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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 258 · 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.

NameDateTime takenScore ___ / 40
  1. 1.Can a triangle have sides of 12 cm, 17 cm and 2 cm? (a) Yes (b) No
  2. 2.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 99° and angle B = 33°. What is angle C (in degrees)?
  5. 5.In triangle ABC, angle A = 52° and angle B = 94°. What is angle C (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  7. 7.Can a triangle have sides of 6 cm, 3 cm and 14 cm? (a) Yes (b) No
  8. 8.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 73° and angle B = 72°. What is angle C (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 61° and 47°. What is the exterior angle (in degrees)?
  12. 12.In triangle ABC, angle A = 82° and angle B = 29°. What is angle C (in degrees)?
  13. 13.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  15. 15.In triangle ABC, angle A = 77° and angle B = 54°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 48° and angle B = 76°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 37° and angle B = 71°. What is angle C (in degrees)?
  18. 18.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  19. 19.In triangle ABC, angle A = 61° and angle B = 27°. What is angle C (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 62° and 21°. What is the exterior angle (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  23. 23.In triangle ABC, angle A = 50° and angle B = 93°. What is angle C (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  26. 26.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  27. 27.An exterior angle of a triangle is 69°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  28. 28.Can a triangle have sides of 12 cm, 3 cm and 12 cm? (a) No (b) Yes
  29. 29.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  32. 32.In triangle ABC, angle A = 85° and angle B = 74°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 24° and angle B = 129°. What is angle C (in degrees)?
  34. 34.An exterior angle of a triangle is 134°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  37. 37.Can a triangle have sides of 8 cm, 5 cm and 2 cm? (a) No (b) Yes
  38. 38.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?

Answer key

  1. No
  2. 33
  3. 42
  4. 48
  5. 34
  6. 80
  7. No
  8. 75
  9. 79
  10. 35
  11. 108
  12. 69
  13. 90
  14. 77
  15. 49
  16. 56
  17. 72
  18. 8
  19. 92
  20. 83
  21. 102
  22. 90
  23. 37
  24. 44
  25. 5
  26. 90
  27. 38
  28. Yes
  29. 80
  30. 51
  31. 14
  32. 21
  33. 27
  34. 62
  35. 64
  36. 25
  37. No
  38. 70
  39. 18
  40. 10

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