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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 848 · 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 triangle ABC, angle A = 62° and angle B = 26°. What is angle C (in degrees)?
  2. 2.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)?
  3. 3.Can a triangle have sides of 22 cm, 12 cm and 8 cm? (a) Yes (b) No
  4. 4.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  7. 7.An exterior angle of a triangle is 128°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  9. 9.In triangle ABC, angle A = 97° and angle B = 32°. What is angle C (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 22° and 52°. What is the exterior angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 23° and 57°. What is the exterior angle (in degrees)?
  15. 15.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  16. 16.In triangle ABC, angle A = 42° and angle B = 79°. What is angle C (in degrees)?
  17. 17.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 21° and 55°. What is the exterior angle (in degrees)?
  19. 19.Can a triangle have sides of 11 cm, 10 cm and 25 cm? (a) Yes (b) No
  20. 20.An exterior angle of a triangle is 138°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  21. 21.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  22. 22.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  23. 23.Can a triangle have sides of 13 cm, 5 cm and 8 cm? (a) Yes (b) No
  24. 24.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 44° each. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 15 cm, 10 cm and 4 cm? (a) No (b) Yes
  27. 27.In triangle ABC, angle A = 81° and angle B = 69°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 10 cm, 5 cm and 9 cm? (a) Yes (b) No
  29. 29.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  33. 33.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)?
  34. 34.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  37. 37.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  39. 39.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  40. 40.In triangle ABC, angle A = 87° and angle B = 61°. What is angle C (in degrees)?

Answer key

  1. 92
  2. 15
  3. No
  4. 69
  5. 75
  6. 45
  7. 67
  8. 90
  9. 51
  10. 74
  11. 54
  12. 77
  13. 70
  14. 80
  15. 33
  16. 59
  17. 32
  18. 76
  19. No
  20. 72
  21. 100
  22. 37
  23. No
  24. 24
  25. 92
  26. No
  27. 30
  28. Yes
  29. 26
  30. 63
  31. 78
  32. 68
  33. 8
  34. 64
  35. 44
  36. 48
  37. 21
  38. 25
  39. 84
  40. 32

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