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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 651 · 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.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  2. 2.Can a triangle have sides of 11 cm, 6 cm and 22 cm? (a) Yes (b) No
  3. 3.Can a triangle have sides of 18 cm, 6 cm and 12 cm? (a) Yes (b) No
  4. 4.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  5. 5.In triangle ABC, angle A = 79° and angle B = 76°. What is angle C (in degrees)?
  6. 6.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 56° and angle B = 102°. What is angle C (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  12. 12.In triangle ABC, angle A = 35° and angle B = 82°. What is angle C (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  14. 14.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)?
  15. 15.Can a triangle have sides of 12 cm, 25 cm and 8 cm? (a) Yes (b) No
  16. 16.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?
  17. 17.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  19. 19.Can a triangle have sides of 25 cm, 9 cm and 11 cm? (a) Yes (b) No
  20. 20.The two interior opposite angles of a triangle are 63° and 43°. What is the exterior angle (in degrees)?
  21. 21.In triangle ABC, angle A = 47° and angle B = 103°. What is angle C (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 57° and angle B = 86°. What is angle C (in degrees)?
  24. 24.In triangle ABC, angle A = 26° and angle B = 34°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 39° and 80°. What is the exterior angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 41° and 61°. What is the exterior angle (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  35. 35.In triangle ABC, angle A = 23° and angle B = 77°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 57° and angle B = 22°. What is angle C (in degrees)?
  37. 37.Can a triangle have sides of 11 cm, 19 cm and 3 cm? (a) Yes (b) No
  38. 38.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  39. 39.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  40. 40.In triangle ABC, angle A = 90° and angle B = 35°. What is angle C (in degrees)?

Answer key

  1. 90
  2. No
  3. No
  4. 75
  5. 25
  6. 36
  7. 72
  8. 76
  9. 22
  10. 20
  11. 77
  12. 63
  13. 13
  14. 3
  15. No
  16. 140
  17. 68
  18. 65
  19. No
  20. 106
  21. 30
  22. 65
  23. 37
  24. 120
  25. 62
  26. 46
  27. 62
  28. 119
  29. 102
  30. 15
  31. 39
  32. 27
  33. 44
  34. 64
  35. 80
  36. 101
  37. No
  38. 90
  39. 8
  40. 55

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