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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 296 · 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 5 cm, 6 cm and 2 cm? (a) No (b) Yes
  2. 2.In triangle ABC, angle A = 65° and angle B = 56°. What is angle C (in degrees)?
  3. 3.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  4. 4.Can a triangle have sides of 13 cm, 7 cm and 6 cm? (a) Yes (b) No
  5. 5.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  8. 8.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 11 cm, 5 cm and 18 cm? (a) No (b) Yes
  11. 11.In triangle ABC, angle A = 58° and angle B = 75°. What is angle C (in degrees)?
  12. 12.In triangle ABC, angle A = 96° and angle B = 23°. What is angle C (in degrees)?
  13. 13.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  15. 15.Can a triangle have sides of 12 cm, 5 cm and 19 cm? (a) Yes (b) No
  16. 16.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 58° and angle B = 20°. What is angle C (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 53° and 58°. What is the exterior angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  21. 21.In triangle ABC, angle A = 57° and angle B = 75°. What is angle C (in degrees)?
  22. 22.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  23. 23.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 16 cm, 9 cm and 9 cm? (a) No (b) Yes
  26. 26.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 40° and 25°. What is the exterior angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  29. 29.Can a triangle have sides of 8 cm, 12 cm and 3 cm? (a) Yes (b) No
  30. 30.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  31. 31.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  32. 32.An exterior angle of a triangle is 55°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  33. 33.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  34. 34.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  35. 35.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  36. 36.In triangle ABC, angle A = 63° and angle B = 90°. What is angle C (in degrees)?
  37. 37.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 47° and angle B = 100°. What is angle C (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 60° and angle B = 20°. What is angle C (in degrees)?

Answer key

  1. Yes
  2. 59
  3. 75
  4. No
  5. 61
  6. 37
  7. 26
  8. 23
  9. 134
  10. No
  11. 47
  12. 61
  13. 24
  14. 33
  15. No
  16. 11
  17. 102
  18. 71
  19. 111
  20. 67
  21. 48
  22. 32
  23. 68
  24. 77
  25. Yes
  26. 120
  27. 65
  28. 40
  29. No
  30. 18
  31. 7
  32. 27
  33. 80
  34. 24
  35. 72
  36. 27
  37. 20
  38. 33
  39. 30
  40. 100

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