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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 648 · 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 two equal angles are 75° each. What is the third angle (in degrees)?
  2. 2.Can a triangle have sides of 10 cm, 20 cm and 5 cm? (a) Yes (b) No
  3. 3.Can a triangle have sides of 2 cm, 10 cm and 10 cm? (a) Yes (b) No
  4. 4.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  5. 5.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  6. 6.Can a triangle have sides of 7 cm, 15 cm and 9 cm? (a) No (b) Yes
  7. 7.In triangle ABC, angle A = 75° and angle B = 72°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 73° and angle B = 57°. What is angle C (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 25° and 34°. What is the exterior angle (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (in degrees)?
  11. 11.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  12. 12.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  13. 13.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  14. 14.Can a triangle have sides of 5 cm, 5 cm and 9 cm? (a) No (b) Yes
  15. 15.The two interior opposite angles of a triangle are 56° and 35°. What is the exterior angle (in degrees)?
  16. 16.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  17. 17.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  18. 18.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  19. 19.In triangle ABC, angle A = 81° and angle B = 33°. What is angle C (in degrees)?
  20. 20.Can a triangle have sides of 2 cm, 12 cm and 13 cm? (a) Yes (b) No
  21. 21.The two interior opposite angles of a triangle are 31° and 23°. What is the exterior angle (in degrees)?
  22. 22.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)?
  23. 23.In an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  25. 25.In triangle ABC, angle A = 94° and angle B = 56°. What is angle C (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  28. 28.In triangle ABC, angle A = 37° and angle B = 81°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 85° and angle B = 22°. What is angle C (in degrees)?
  30. 30.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  31. 31.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 60° and 53°. What is the exterior angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  36. 36.The two interior opposite angles of a triangle are 71° and 75°. What is the exterior angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  38. 38.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 61° each. What is the third angle (in degrees)?

Answer key

  1. 30
  2. No
  3. Yes
  4. 72
  5. 55
  6. Yes
  7. 33
  8. 50
  9. 59
  10. 68
  11. 53
  12. 36
  13. 104
  14. Yes
  15. 91
  16. 15
  17. 50
  18. 25
  19. 66
  20. Yes
  21. 54
  22. 15
  23. 96
  24. 78
  25. 30
  26. 138
  27. 46
  28. 62
  29. 73
  30. 36
  31. 51
  32. 113
  33. 48
  34. 100
  35. 17
  36. 146
  37. 37
  38. 26
  39. 51
  40. 58

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