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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 658 · 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 10 cm, 7 cm and 14 cm? (a) Yes (b) No
  2. 2.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  3. 3.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  5. 5.Can a triangle have sides of 8 cm, 12 cm and 21 cm? (a) No (b) Yes
  6. 6.The two interior opposite angles of a triangle are 61° and 69°. What is the exterior angle (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  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.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  12. 12.Can a triangle have sides of 11 cm, 7 cm and 7 cm? (a) No (b) Yes
  13. 13.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  14. 14.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 59° and 73°. What is the exterior angle (in degrees)?
  19. 19.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  21. 21.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 62° and 22°. What is the exterior angle (in degrees)?
  23. 23.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  24. 24.Can a triangle have sides of 10 cm, 8 cm and 3 cm? (a) Yes (b) No
  25. 25.Can a triangle have sides of 9 cm, 11 cm and 10 cm? (a) No (b) Yes
  26. 26.In triangle ABC, angle A = 34° and angle B = 43°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 4 cm, 10 cm and 18 cm? (a) Yes (b) No
  28. 28.In triangle ABC, angle A = 25° and angle B = 105°. What is angle C (in degrees)?
  29. 29.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)?
  30. 30.Can a triangle have sides of 11 cm, 9 cm and 21 cm? (a) Yes (b) No
  31. 31.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  33. 33.The two interior opposite angles of a triangle are 33° and 27°. What is the exterior angle (in degrees)?
  34. 34.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  35. 35.In triangle ABC, angle A = 39° and angle B = 79°. What is angle C (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  37. 37.In triangle ABC, angle A = 42° and angle B = 25°. What is angle C (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  40. 40.Can a triangle have sides of 5 cm, 8 cm and 4 cm? (a) No (b) Yes

Answer key

  1. Yes
  2. 70
  3. 70
  4. 67
  5. No
  6. 130
  7. 20
  8. 28
  9. 17
  10. 30
  11. 31
  12. Yes
  13. 70
  14. 45
  15. 36
  16. 90
  17. 20
  18. 132
  19. 48
  20. 25
  21. 20
  22. 84
  23. 60
  24. Yes
  25. Yes
  26. 103
  27. No
  28. 50
  29. 4
  30. No
  31. 25
  32. 10
  33. 60
  34. 74
  35. 62
  36. 13
  37. 113
  38. 30
  39. 59
  40. Yes

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