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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 442 · 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.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  3. 3.Can a triangle have sides of 7 cm, 6 cm and 16 cm? (a) Yes (b) No
  4. 4.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  5. 5.Can a triangle have sides of 4 cm, 12 cm and 7 cm? (a) No (b) Yes
  6. 6.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  7. 7.In triangle ABC, angle A = 39° and angle B = 59°. What is angle C (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 22° and 45°. What is the exterior 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.Can a triangle have sides of 10 cm, 11 cm and 22 cm? (a) Yes (b) No
  11. 11.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  12. 12.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  13. 13.Can a triangle have sides of 19 cm, 12 cm and 7 cm? (a) No (b) Yes
  14. 14.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  15. 15.The two interior opposite angles of a triangle are 40° and 35°. What is the exterior angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 22° and 57°. What is the exterior angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 10 cm, 12 cm and 8 cm? (a) Yes (b) No
  20. 20.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)?
  21. 21.Can a triangle have sides of 9 cm, 22 cm and 12 cm? (a) Yes (b) No
  22. 22.In triangle ABC, angle A = 36° and angle B = 20°. What is angle C (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 37° and angle B = 49°. What is angle C (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 56° and 52°. What is the exterior angle (in degrees)?
  28. 28.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 32° and 34°. What is the exterior angle (in degrees)?
  31. 31.An exterior angle of a triangle is 153°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  32. 32.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  33. 33.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  34. 34.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 110°. What is each of the other two angles (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  37. 37.In triangle ABC, angle A = 56° and angle B = 70°. What is angle C (in degrees)?
  38. 38.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 25° and 41°. What is the exterior angle (in degrees)?

Answer key

  1. 39
  2. 38
  3. No
  4. 18
  5. No
  6. 13
  7. 82
  8. 67
  9. 37
  10. No
  11. 36
  12. 23
  13. No
  14. 12
  15. 75
  16. 75
  17. 79
  18. 13
  19. Yes
  20. 24
  21. No
  22. 124
  23. 46
  24. 94
  25. 77
  26. 90
  27. 108
  28. 50
  29. 29
  30. 66
  31. 76
  32. 5
  33. 31
  34. 32
  35. 35
  36. 14
  37. 54
  38. 76
  39. 61
  40. 66

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