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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 614 · 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 a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  2. 2.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)?
  3. 3.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  4. 4.The two interior opposite angles of a triangle are 61° and 62°. What is the exterior angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  9. 9.Can a triangle have sides of 3 cm, 9 cm and 8 cm? (a) No (b) Yes
  10. 10.The two interior opposite angles of a triangle are 27° and 71°. What is the exterior angle (in degrees)?
  11. 11.In triangle ABC, angle A = 47° and angle B = 29°. What is angle C (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 24° and 69°. What is the exterior angle (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 62° each. What is the third angle (in degrees)?
  14. 14.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  15. 15.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  17. 17.In triangle ABC, angle A = 23° and angle B = 32°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 54° and angle B = 66°. What is angle C (in degrees)?
  19. 19.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 67° and angle B = 63°. What is angle C (in degrees)?
  22. 22.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)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  28. 28.Can a triangle have sides of 2 cm, 7 cm and 2 cm? (a) Yes (b) No
  29. 29.In triangle ABC, angle A = 26° and angle B = 25°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 65° and angle B = 41°. What is angle C (in degrees)?
  31. 31.Can a triangle have sides of 2 cm, 3 cm and 10 cm? (a) Yes (b) No
  32. 32.Can a triangle have sides of 6 cm, 15 cm and 9 cm? (a) No (b) Yes
  33. 33.In triangle ABC, angle A = 71° and angle B = 35°. What is angle C (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  35. 35.An exterior angle of a triangle is 139°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  36. 36.Can a triangle have sides of 12 cm, 21 cm and 8 cm? (a) No (b) Yes
  37. 37.In triangle ABC, angle A = 93° and angle B = 46°. What is angle C (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  39. 39.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?

Answer key

  1. 78
  2. 8
  3. 30
  4. 123
  5. 18
  6. 58
  7. 23
  8. 17
  9. Yes
  10. 98
  11. 104
  12. 93
  13. 56
  14. 35
  15. 72
  16. 10
  17. 125
  18. 60
  19. 43
  20. 19
  21. 50
  22. 7
  23. 73
  24. 136
  25. 70
  26. 80
  27. 61
  28. No
  29. 129
  30. 74
  31. No
  32. No
  33. 74
  34. 52
  35. 70
  36. No
  37. 41
  38. 26
  39. 66
  40. 10

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