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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 132 · 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.Can a triangle have sides of 4 cm, 2 cm and 7 cm? (a) No (b) Yes
  2. 2.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 79° and 21°. What is the exterior angle (in degrees)?
  4. 4.Can a triangle have sides of 4 cm, 8 cm and 4 cm? (a) No (b) Yes
  5. 5.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  6. 6.The two interior opposite angles of a triangle are 34° and 24°. What is the exterior angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  8. 8.In triangle ABC, angle A = 27° and angle B = 83°. What is angle C (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  10. 10.The two interior opposite angles of a triangle are 77° and 41°. What is the exterior angle (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 56° and 68°. What is the exterior angle (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 61° each. What is the third angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  15. 15.Can a triangle have sides of 9 cm, 12 cm and 21 cm? (a) Yes (b) No
  16. 16.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  17. 17.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 30° and 52°. What is the exterior angle (in degrees)?
  19. 19.Can a triangle have sides of 11 cm, 5 cm and 20 cm? (a) No (b) Yes
  20. 20.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  23. 23.Can a triangle have sides of 12 cm, 6 cm and 9 cm? (a) No (b) Yes
  24. 24.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 85° and angle B = 34°. What is angle C (in degrees)?
  28. 28.In triangle ABC, angle A = 57° and angle B = 67°. What is angle C (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  30. 30.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  31. 31.Can a triangle have sides of 9 cm, 23 cm and 11 cm? (a) No (b) Yes
  32. 32.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  33. 33.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  34. 34.An exterior angle of a triangle is 120°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 30° and 44°. What is the exterior angle (in degrees)?
  36. 36.In triangle ABC, angle A = 21° and angle B = 90°. What is angle C (in degrees)?
  37. 37.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  40. 40.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?

Answer key

  1. No
  2. 43
  3. 100
  4. No
  5. 15
  6. 58
  7. 30
  8. 70
  9. 26
  10. 118
  11. 124
  12. 58
  13. 13
  14. 11
  15. No
  16. 50
  17. 24
  18. 82
  19. No
  20. 66
  21. 90
  22. 17
  23. Yes
  24. 76
  25. 18
  26. 69
  27. 61
  28. 56
  29. 100
  30. 4
  31. No
  32. 25
  33. 33
  34. 70
  35. 74
  36. 69
  37. 75
  38. 80
  39. 90
  40. 55

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