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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 29 · 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 4 cm, 2 cm and 4 cm? (a) No (b) Yes
  2. 2.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 60° and angle B = 41°. What is angle C (in degrees)?
  4. 4.Can a triangle have sides of 10 cm, 13 cm and 11 cm? (a) No (b) Yes
  5. 5.The two interior opposite angles of a triangle are 62° and 32°. What is the exterior angle (in degrees)?
  6. 6.Can a triangle have sides of 11 cm, 11 cm and 6 cm? (a) No (b) Yes
  7. 7.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  10. 10.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  15. 15.In triangle ABC, angle A = 67° and angle B = 44°. What is angle C (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  17. 17.Can a triangle have sides of 11 cm, 6 cm and 18 cm? (a) Yes (b) No
  18. 18.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  19. 19.In triangle ABC, angle A = 81° and angle B = 49°. What is angle C (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  21. 21.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  22. 22.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  24. 24.In triangle ABC, angle A = 31° and angle B = 119°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 43° and angle B = 104°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  27. 27.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 62° each. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 26° and 47°. What is the exterior angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  33. 33.In triangle ABC, angle A = 47° and angle B = 93°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 9 cm, 2 cm and 3 cm? (a) Yes (b) No
  35. 35.Can a triangle have sides of 10 cm, 24 cm and 10 cm? (a) No (b) Yes
  36. 36.In triangle ABC, angle A = 81° and angle B = 26°. What is angle C (in degrees)?
  37. 37.Can a triangle have sides of 4 cm, 10 cm and 6 cm? (a) No (b) Yes
  38. 38.Can a triangle have sides of 10 cm, 11 cm and 24 cm? (a) No (b) Yes
  39. 39.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  40. 40.In triangle ABC, angle A = 43° and angle B = 63°. What is angle C (in degrees)?

Answer key

  1. Yes
  2. 70
  3. 79
  4. Yes
  5. 94
  6. Yes
  7. 62
  8. 100
  9. 120
  10. 24
  11. 59
  12. 12
  13. 47
  14. 30
  15. 69
  16. 25
  17. No
  18. 64
  19. 50
  20. 24
  21. 34
  22. 60
  23. 90
  24. 30
  25. 33
  26. 14
  27. 15
  28. 22
  29. 56
  30. 132
  31. 73
  32. 72
  33. 40
  34. No
  35. No
  36. 73
  37. No
  38. No
  39. 27
  40. 74

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