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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 873 · 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.

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  1. 1.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  2. 2.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)?
  3. 3.In triangle ABC, angle A = 55° and angle B = 34°. What is angle C (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  5. 5.In triangle ABC, angle A = 29° and angle B = 77°. What is angle C (in degrees)?
  6. 6.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  7. 7.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  8. 8.An exterior angle of a triangle is 126°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  9. 9.In triangle ABC, angle A = 79° and angle B = 38°. What is angle C (in degrees)?
  10. 10.Can a triangle have sides of 18 cm, 7 cm and 6 cm? (a) Yes (b) No
  11. 11.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  13. 13.Can a triangle have sides of 9 cm, 21 cm and 12 cm? (a) No (b) Yes
  14. 14.The two interior opposite angles of a triangle are 65° and 59°. What is the exterior angle (in degrees)?
  15. 15.Can a triangle have sides of 8 cm, 4 cm and 4 cm? (a) No (b) Yes
  16. 16.An exterior angle of a triangle is 127°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  17. 17.Can a triangle have sides of 4 cm, 11 cm and 6 cm? (a) No (b) Yes
  18. 18.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  21. 21.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  22. 22.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  23. 23.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 7 cm, 4 cm and 15 cm? (a) Yes (b) No
  27. 27.In triangle ABC, angle A = 55° and angle B = 94°. What is angle C (in degrees)?
  28. 28.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  29. 29.In triangle ABC, angle A = 47° and angle B = 66°. What is angle C (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 38° and 73°. What is the exterior angle (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 56° each. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 59° and angle B = 24°. What is angle C (in degrees)?
  36. 36.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)?
  37. 37.In triangle ABC, angle A = 21° and angle B = 88°. What is angle C (in degrees)?
  38. 38.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  40. 40.An exterior angle of a triangle is 65°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?

Answer key

  1. 36
  2. 24
  3. 91
  4. 65
  5. 74
  6. 17
  7. 38
  8. 69
  9. 63
  10. No
  11. 45
  12. 39
  13. No
  14. 124
  15. No
  16. 63
  17. No
  18. 47
  19. 80
  20. 45
  21. 56
  22. 40
  23. 76
  24. 59
  25. 134
  26. No
  27. 31
  28. 120
  29. 67
  30. 111
  31. 70
  32. 73
  33. 51
  34. 68
  35. 97
  36. 15
  37. 71
  38. 50
  39. 53
  40. 44

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