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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 727 · 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 8 cm, 11 cm and 10 cm? (a) No (b) Yes
  2. 2.The two interior opposite angles of a triangle are 34° and 24°. What is the exterior angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  4. 4.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  5. 5.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  6. 6.In triangle ABC, angle A = 25° and angle B = 99°. What is angle C (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 54° and 29°. What is the exterior angle (in degrees)?
  8. 8.Can a triangle have sides of 5 cm, 9 cm and 3 cm? (a) Yes (b) No
  9. 9.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 9 cm, 18 cm and 8 cm? (a) Yes (b) No
  11. 11.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 46° and 33°. What is the exterior angle (in degrees)?
  15. 15.Can a triangle have sides of 9 cm, 6 cm and 19 cm? (a) No (b) Yes
  16. 16.In triangle ABC, angle A = 61° and angle B = 57°. What is angle C (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  18. 18.Can a triangle have sides of 6 cm, 18 cm and 12 cm? (a) Yes (b) No
  19. 19.The two interior opposite angles of a triangle are 29° and 75°. What is the exterior angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  23. 23.An exterior angle of a triangle is 48°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  24. 24.Can a triangle have sides of 7 cm, 8 cm and 15 cm? (a) No (b) Yes
  25. 25.Can a triangle have sides of 3 cm, 3 cm and 6 cm? (a) No (b) Yes
  26. 26.In triangle ABC, angle A = 29° and angle B = 21°. What is angle C (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  28. 28.Can a triangle have sides of 12 cm, 4 cm and 20 cm? (a) No (b) Yes
  29. 29.In triangle ABC, angle A = 66° and angle B = 40°. What is angle C (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  33. 33.Can a triangle have sides of 20 cm, 10 cm and 10 cm? (a) Yes (b) No
  34. 34.In triangle ABC, angle A = 70° and angle B = 53°. What is angle C (in degrees)?
  35. 35.In triangle ABC, angle A = 83° and angle B = 47°. What is angle C (in degrees)?
  36. 36.Can a triangle have sides of 22 cm, 12 cm and 10 cm? (a) Yes (b) No
  37. 37.Can a triangle have sides of 4 cm, 6 cm and 7 cm? (a) Yes (b) No
  38. 38.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  39. 39.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)?
  40. 40.The two interior opposite angles of a triangle are 48° and 48°. What is the exterior angle (in degrees)?

Answer key

  1. Yes
  2. 58
  3. 13
  4. 24
  5. 20
  6. 56
  7. 83
  8. No
  9. 19
  10. No
  11. 61
  12. 31
  13. 17
  14. 79
  15. No
  16. 62
  17. 17
  18. No
  19. 104
  20. 90
  21. 90
  22. 49
  23. 20
  24. No
  25. No
  26. 130
  27. 53
  28. No
  29. 74
  30. 32
  31. 36
  32. 30
  33. No
  34. 57
  35. 50
  36. No
  37. Yes
  38. 78
  39. 15
  40. 96

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