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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 345 · 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 7 cm, 4 cm and 5 cm? (a) No (b) Yes
  2. 2.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 52° and angle B = 79°. What is angle C (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  5. 5.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  6. 6.In triangle ABC, angle A = 92° and angle B = 30°. What is angle C (in degrees)?
  7. 7.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  8. 8.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  9. 9.Can a triangle have sides of 2 cm, 8 cm and 15 cm? (a) No (b) Yes
  10. 10.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)?
  11. 11.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  12. 12.In triangle ABC, angle A = 97° and angle B = 32°. What is angle C (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  14. 14.In triangle ABC, angle A = 20° and angle B = 37°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 99° and angle B = 26°. What is angle C (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  17. 17.Can a triangle have sides of 5 cm, 6 cm and 7 cm? (a) No (b) Yes
  18. 18.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  20. 20.Can a triangle have sides of 10 cm, 24 cm and 12 cm? (a) No (b) Yes
  21. 21.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  22. 22.In triangle ABC, angle A = 46° and angle B = 83°. What is angle C (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 46° and 80°. What is the exterior angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  26. 26.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 78° and 45°. What is the exterior angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  30. 30.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 22° and 32°. What is the exterior angle (in degrees)?
  32. 32.In triangle ABC, angle A = 97° and angle B = 23°. What is angle C (in degrees)?
  33. 33.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  35. 35.In triangle ABC, angle A = 30° and angle B = 58°. What is angle C (in degrees)?
  36. 36.Can a triangle have sides of 11 cm, 8 cm and 19 cm? (a) No (b) Yes
  37. 37.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 89° and angle B = 32°. What is angle C (in degrees)?

Answer key

  1. Yes
  2. 40
  3. 49
  4. 17
  5. 68
  6. 58
  7. 24
  8. 90
  9. No
  10. 15
  11. 15
  12. 51
  13. 26
  14. 123
  15. 55
  16. 37
  17. Yes
  18. 19
  19. 31
  20. No
  21. 29
  22. 51
  23. 126
  24. 68
  25. 17
  26. 100
  27. 123
  28. 36
  29. 13
  30. 28
  31. 54
  32. 60
  33. 72
  34. 100
  35. 92
  36. No
  37. 86
  38. 36
  39. 78
  40. 59

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