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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 763 · 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.

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  1. 1.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  3. 3.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  4. 4.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  6. 6.In triangle ABC, angle A = 66° and angle B = 39°. What is angle C (in degrees)?
  7. 7.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  8. 8.In triangle ABC, angle A = 77° and angle B = 43°. What is angle C (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  11. 11.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  12. 12.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  15. 15.In triangle ABC, angle A = 49° and angle B = 94°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 81° and angle B = 56°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 22° and 36°. What is the exterior angle (in degrees)?
  20. 20.In triangle ABC, angle A = 22° and angle B = 111°. What is angle C (in degrees)?
  21. 21.Can a triangle have sides of 4 cm, 8 cm and 8 cm? (a) No (b) Yes
  22. 22.Can a triangle have sides of 13 cm, 10 cm and 11 cm? (a) No (b) Yes
  23. 23.In triangle ABC, angle A = 93° and angle B = 63°. What is angle C (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 154°. What is each of the other two angles (in degrees)?
  25. 25.In triangle ABC, angle A = 60° and angle B = 42°. What is angle C (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  27. 27.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  28. 28.Can a triangle have sides of 8 cm, 6 cm and 5 cm? (a) No (b) Yes
  29. 29.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  30. 30.The two interior opposite angles of a triangle are 68° and 67°. What is the exterior angle (in degrees)?
  31. 31.An exterior angle of a triangle is 59°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  32. 32.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  33. 33.In triangle ABC, angle A = 25° and angle B = 25°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 3 cm, 2 cm and 3 cm? (a) No (b) Yes
  35. 35.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  36. 36.Can a triangle have sides of 21 cm, 10 cm and 9 cm? (a) Yes (b) No
  37. 37.The two interior opposite angles of a triangle are 28° and 30°. What is the exterior angle (in degrees)?
  38. 38.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)?
  39. 39.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  40. 40.Can a triangle have sides of 16 cm, 6 cm and 8 cm? (a) Yes (b) No

Answer key

  1. 62
  2. 75
  3. 15
  4. 90
  5. 90
  6. 75
  7. 40
  8. 60
  9. 74
  10. 25
  11. 72
  12. 35
  13. 36
  14. 80
  15. 37
  16. 43
  17. 65
  18. 21
  19. 58
  20. 47
  21. Yes
  22. Yes
  23. 24
  24. 13
  25. 78
  26. 25
  27. 45
  28. Yes
  29. 26
  30. 135
  31. 30
  32. 41
  33. 130
  34. Yes
  35. 13
  36. No
  37. 58
  38. 15
  39. 6
  40. No

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