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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 44 · 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 2 cm, 4 cm and 3 cm? (a) Yes (b) No
  2. 2.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  3. 3.The two interior opposite angles of a triangle are 55° and 26°. What is the exterior angle (in degrees)?
  4. 4.In triangle ABC, angle A = 97° and angle B = 40°. What is angle C (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  6. 6.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 64° and angle B = 66°. What is angle C (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  16. 16.The two interior opposite angles of a triangle are 27° and 67°. What is the exterior angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  18. 18.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)?
  19. 19.In triangle ABC, angle A = 45° and angle B = 54°. What is angle C (in degrees)?
  20. 20.Can a triangle have sides of 12 cm, 10 cm and 23 cm? (a) No (b) Yes
  21. 21.Can a triangle have sides of 9 cm, 8 cm and 5 cm? (a) No (b) Yes
  22. 22.In triangle ABC, angle A = 66° and angle B = 45°. What is angle C (in degrees)?
  23. 23.An exterior angle of a triangle is 59°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  24. 24.In triangle ABC, angle A = 98° and angle B = 61°. What is angle C (in degrees)?
  25. 25.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  26. 26.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  27. 27.In triangle ABC, angle A = 76° and angle B = 63°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 4 cm, 4 cm and 4 cm? (a) No (b) Yes
  29. 29.Can a triangle have sides of 21 cm, 12 cm and 7 cm? (a) Yes (b) No
  30. 30.An exterior angle of a triangle is 55°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  31. 31.Can a triangle have sides of 11 cm, 9 cm and 5 cm? (a) No (b) Yes
  32. 32.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  34. 34.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  35. 35.Can a triangle have sides of 8 cm, 4 cm and 7 cm? (a) No (b) Yes
  36. 36.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  38. 38.Can a triangle have sides of 12 cm, 8 cm and 21 cm? (a) No (b) Yes
  39. 39.The two interior opposite angles of a triangle are 61° and 56°. What is the exterior angle (in degrees)?
  40. 40.In triangle ABC, angle A = 20° and angle B = 92°. What is angle C (in degrees)?

Answer key

  1. Yes
  2. 25
  3. 81
  4. 43
  5. 74
  6. 36
  7. 70
  8. 128
  9. 37
  10. 50
  11. 38
  12. 30
  13. 60
  14. 12
  15. 17
  16. 94
  17. 36
  18. 24
  19. 81
  20. No
  21. Yes
  22. 69
  23. 31
  24. 21
  25. 15
  26. 20
  27. 41
  28. Yes
  29. No
  30. 31
  31. Yes
  32. 28
  33. 36
  34. 17
  35. Yes
  36. 70
  37. 36
  38. No
  39. 117
  40. 68

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