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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 13 · 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.Can a triangle have sides of 3 cm, 8 cm and 10 cm? (a) No (b) Yes
  2. 2.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  3. 3.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  5. 5.In triangle ABC, angle A = 25° and angle B = 68°. What is angle C (in degrees)?
  6. 6.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  7. 7.In triangle ABC, angle A = 24° and angle B = 75°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 24° and angle B = 135°. What is angle C (in degrees)?
  9. 9.In triangle ABC, angle A = 84° and angle B = 56°. What is angle C (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  11. 11.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  12. 12.Can a triangle have sides of 15 cm, 10 cm and 11 cm? (a) No (b) Yes
  13. 13.In triangle ABC, angle A = 24° and angle B = 52°. What is angle C (in degrees)?
  14. 14.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  15. 15.Can a triangle have sides of 22 cm, 9 cm and 9 cm? (a) No (b) Yes
  16. 16.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  17. 17.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  18. 18.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)?
  19. 19.In triangle ABC, angle A = 80° and angle B = 61°. What is angle C (in degrees)?
  20. 20.Can a triangle have sides of 7 cm, 4 cm and 6 cm? (a) No (b) Yes
  21. 21.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  22. 22.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 74° and angle B = 83°. What is angle C (in degrees)?
  25. 25.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  26. 26.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  28. 28.Can a triangle have sides of 4 cm, 9 cm and 9 cm? (a) Yes (b) No
  29. 29.Can a triangle have sides of 14 cm, 3 cm and 10 cm? (a) Yes (b) No
  30. 30.In triangle ABC, angle A = 97° and angle B = 52°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 45° and angle B = 106°. What is angle C (in degrees)?
  32. 32.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 110°. What is each of the other two angles (in degrees)?
  37. 37.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  38. 38.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?

Answer key

  1. Yes
  2. 22
  3. 51
  4. 75
  5. 87
  6. 49
  7. 81
  8. 21
  9. 40
  10. 30
  11. 25
  12. Yes
  13. 104
  14. 72
  15. No
  16. 36
  17. 78
  18. 7
  19. 39
  20. Yes
  21. 25
  22. 10
  23. 15
  24. 23
  25. 72
  26. 45
  27. 52
  28. Yes
  29. No
  30. 31
  31. 29
  32. 71
  33. 62
  34. 124
  35. 17
  36. 35
  37. 48
  38. 46
  39. 100
  40. 27

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