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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 427 · 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.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  2. 2.In triangle ABC, angle A = 83° and angle B = 59°. What is angle C (in degrees)?
  3. 3.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  4. 4.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  7. 7.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  9. 9.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  10. 10.Can a triangle have sides of 2 cm, 3 cm and 2 cm? (a) Yes (b) No
  11. 11.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  14. 14.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 91° and angle B = 47°. What is angle C (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  22. 22.Can a triangle have sides of 11 cm, 5 cm and 10 cm? (a) No (b) Yes
  23. 23.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 8 cm, 9 cm and 12 cm? (a) No (b) Yes
  25. 25.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 77° and 34°. What is the exterior angle (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  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.Can a triangle have sides of 9 cm, 5 cm and 12 cm? (a) Yes (b) No
  30. 30.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)?
  31. 31.In triangle ABC, angle A = 99° and angle B = 40°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 45° and angle B = 91°. What is angle C (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  34. 34.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  35. 35.In triangle ABC, angle A = 98° and angle B = 27°. What is angle C (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 86°. What is each of the other two angles (in degrees)?
  37. 37.Can a triangle have sides of 4 cm, 9 cm and 10 cm? (a) No (b) Yes
  38. 38.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?

Answer key

  1. 63
  2. 38
  3. 49
  4. 90
  5. 41
  6. 72
  7. 54
  8. 17
  9. 26
  10. Yes
  11. 64
  12. 26
  13. 13
  14. 42
  15. 84
  16. 36
  17. 42
  18. 36
  19. 49
  20. 19
  21. 90
  22. Yes
  23. 132
  24. Yes
  25. 70
  26. 111
  27. 20
  28. 39
  29. Yes
  30. 3
  31. 41
  32. 44
  33. 20
  34. 76
  35. 55
  36. 47
  37. Yes
  38. 54
  39. 90
  40. 80

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