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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 77 · 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.The two interior opposite angles of a triangle are 68° and 58°. What is the exterior angle (in degrees)?
  2. 2.Can a triangle have sides of 8 cm, 20 cm and 10 cm? (a) No (b) Yes
  3. 3.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 94° and angle B = 52°. What is angle C (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles (in degrees)?
  6. 6.In triangle ABC, angle A = 40° and angle B = 55°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 29° and angle B = 45°. What is angle C (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  10. 10.In triangle ABC, angle A = 43° and angle B = 21°. What is angle C (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  16. 16.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)?
  17. 17.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  18. 18.In triangle ABC, angle A = 21° and angle B = 128°. What is angle C (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  21. 21.In triangle ABC, angle A = 75° and angle B = 28°. What is angle C (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 44° each. What is the third angle (in degrees)?
  23. 23.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)?
  24. 24.The two interior opposite angles of a triangle are 51° and 55°. What is the exterior angle (in degrees)?
  25. 25.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  26. 26.Can a triangle have sides of 9 cm, 9 cm and 20 cm? (a) Yes (b) No
  27. 27.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  28. 28.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  29. 29.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  31. 31.An exterior angle of a triangle is 49°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 69° and 63°. What is the exterior angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 39° and angle B = 59°. What is angle C (in degrees)?
  35. 35.Can a triangle have sides of 17 cm, 12 cm and 8 cm? (a) No (b) Yes
  36. 36.In triangle ABC, angle A = 56° and angle B = 99°. What is angle C (in degrees)?
  37. 37.In triangle ABC, angle A = 76° and angle B = 56°. What is angle C (in degrees)?
  38. 38.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  39. 39.In triangle ABC, angle A = 64° and angle B = 60°. What is angle C (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?

Answer key

  1. 126
  2. No
  3. 49
  4. 34
  5. 30
  6. 85
  7. 106
  8. 13
  9. 27
  10. 116
  11. 45
  12. 58
  13. 72
  14. 100
  15. 50
  16. 15
  17. 51
  18. 31
  19. 106
  20. 100
  21. 77
  22. 92
  23. 8
  24. 106
  25. 12
  26. No
  27. 58
  28. 74
  29. 45
  30. 67
  31. 22
  32. 132
  33. 76
  34. 82
  35. Yes
  36. 25
  37. 48
  38. 29
  39. 56
  40. 77

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