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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 434 · 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.The two interior opposite angles of a triangle are 35° and 23°. What is the exterior angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  3. 3.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  4. 4.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  5. 5.The two interior opposite angles of a triangle are 35° and 52°. What is the exterior angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  7. 7.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  8. 8.Can a triangle have sides of 9 cm, 10 cm and 3 cm? (a) Yes (b) No
  9. 9.In triangle ABC, angle A = 69° and angle B = 63°. What is angle C (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  11. 11.Can a triangle have sides of 2 cm, 9 cm and 3 cm? (a) No (b) Yes
  12. 12.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  13. 13.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  16. 16.In triangle ABC, angle A = 73° and angle B = 36°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 11 cm, 25 cm and 10 cm? (a) No (b) Yes
  20. 20.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  21. 21.Can a triangle have sides of 17 cm, 12 cm and 10 cm? (a) Yes (b) No
  22. 22.Can a triangle have sides of 8 cm, 7 cm and 2 cm? (a) No (b) Yes
  23. 23.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 11 cm, 6 cm and 4 cm? (a) Yes (b) No
  25. 25.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 51° and 27°. What is the exterior angle (in degrees)?
  27. 27.In triangle ABC, angle A = 81° and angle B = 49°. What is angle C (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  29. 29.The two interior opposite angles of a triangle are 46° and 50°. What is the exterior angle (in degrees)?
  30. 30.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 66° and angle B = 84°. What is angle C (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 39° and 30°. What is the exterior angle (in degrees)?
  34. 34.Can a triangle have sides of 8 cm, 3 cm and 3 cm? (a) No (b) Yes
  35. 35.Can a triangle have sides of 9 cm, 6 cm and 19 cm? (a) No (b) Yes
  36. 36.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  37. 37.The two interior opposite angles of a triangle are 33° and 69°. What is the exterior angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  40. 40.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?

Answer key

  1. 58
  2. 75
  3. 23
  4. 3
  5. 87
  6. 29
  7. 31
  8. Yes
  9. 48
  10. 72
  11. No
  12. 8
  13. 84
  14. 72
  15. 77
  16. 71
  17. 24
  18. 56
  19. No
  20. 25
  21. Yes
  22. Yes
  23. 138
  24. No
  25. 59
  26. 78
  27. 50
  28. 39
  29. 96
  30. 64
  31. 73
  32. 30
  33. 69
  34. No
  35. No
  36. 5
  37. 102
  38. 90
  39. 25
  40. 63

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