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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 24 · 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 51° and 33°. What is the exterior angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  3. 3.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  4. 4.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  5. 5.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  6. 6.In triangle ABC, angle A = 58° and angle B = 86°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 74° and angle B = 54°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 44° and angle B = 43°. What is angle C (in degrees)?
  9. 9.In triangle ABC, angle A = 83° and angle B = 64°. What is angle C (in degrees)?
  10. 10.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  11. 11.Can a triangle have sides of 17 cm, 7 cm and 11 cm? (a) Yes (b) No
  12. 12.In triangle ABC, angle A = 98° and angle B = 46°. What is angle C (in degrees)?
  13. 13.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  14. 14.In triangle ABC, angle A = 69° and angle B = 86°. What is angle C (in degrees)?
  15. 15.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  16. 16.In triangle ABC, angle A = 61° and angle B = 59°. What is angle C (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  18. 18.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 32° and 49°. What is the exterior angle (in degrees)?
  20. 20.Can a triangle have sides of 8 cm, 9 cm and 6 cm? (a) No (b) Yes
  21. 21.Can a triangle have sides of 8 cm, 7 cm and 17 cm? (a) Yes (b) No
  22. 22.Can a triangle have sides of 6 cm, 6 cm and 17 cm? (a) Yes (b) No
  23. 23.Can a triangle have sides of 15 cm, 3 cm and 12 cm? (a) No (b) Yes
  24. 24.An exterior angle of a triangle is 136°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  25. 25.Can a triangle have sides of 6 cm, 4 cm and 5 cm? (a) No (b) Yes
  26. 26.The two interior opposite angles of a triangle are 34° and 53°. What is the exterior angle (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  28. 28.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  30. 30.In triangle ABC, angle A = 24° and angle B = 78°. What is angle C (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 46° and 55°. What is the exterior angle (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  34. 34.The two interior opposite angles of a triangle are 65° and 25°. What is the exterior angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 54° and 55°. What is the exterior angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 79° and 21°. What is the exterior angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  39. 39.In triangle ABC, angle A = 76° and angle B = 32°. What is angle C (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?

Answer key

  1. 84
  2. 36
  3. 9
  4. 46
  5. 56
  6. 36
  7. 52
  8. 93
  9. 33
  10. 80
  11. Yes
  12. 36
  13. 34
  14. 25
  15. 80
  16. 60
  17. 25
  18. 34
  19. 81
  20. Yes
  21. No
  22. No
  23. No
  24. 65
  25. Yes
  26. 87
  27. 17
  28. 71
  29. 90
  30. 78
  31. 68
  32. 101
  33. 15
  34. 90
  35. 109
  36. 100
  37. 60
  38. 122
  39. 72
  40. 20

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