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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 39 · 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 12 cm, 10 cm and 25 cm? (a) No (b) Yes
  2. 2.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  3. 3.Can a triangle have sides of 3 cm, 3 cm and 2 cm? (a) Yes (b) No
  4. 4.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  6. 6.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 154°. What is each of the other two angles (in degrees)?
  9. 9.In triangle ABC, angle A = 65° and angle B = 44°. What is angle C (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  14. 14.In triangle ABC, angle A = 32° and angle B = 54°. What is angle C (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  16. 16.The two interior opposite angles of a triangle are 57° and 45°. What is the exterior angle (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  18. 18.An exterior angle of a triangle is 46°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  21. 21.Can a triangle have sides of 11 cm, 18 cm and 2 cm? (a) Yes (b) No
  22. 22.In triangle ABC, angle A = 69° and angle B = 39°. What is angle C (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  24. 24.In triangle ABC, angle A = 22° and angle B = 82°. What is angle C (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 95° and angle B = 30°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 6 cm, 12 cm and 10 cm? (a) No (b) Yes
  28. 28.Can a triangle have sides of 2 cm, 9 cm and 7 cm? (a) No (b) Yes
  29. 29.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 49° and 58°. What is the exterior angle (in degrees)?
  31. 31.In triangle ABC, angle A = 99° and angle B = 32°. What is angle C (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  33. 33.Can a triangle have sides of 9 cm, 10 cm and 3 cm? (a) No (b) Yes
  34. 34.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  36. 36.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  38. 38.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  39. 39.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  40. 40.In triangle ABC, angle A = 20° and angle B = 103°. What is angle C (in degrees)?

Answer key

  1. No
  2. 18
  3. Yes
  4. 126
  5. 17
  6. 27
  7. 20
  8. 13
  9. 71
  10. 25
  11. 59
  12. 32
  13. 32
  14. 94
  15. 20
  16. 102
  17. 72
  18. 22
  19. 18
  20. 72
  21. No
  22. 72
  23. 25
  24. 76
  25. 40
  26. 55
  27. Yes
  28. No
  29. 15
  30. 107
  31. 49
  32. 79
  33. Yes
  34. 39
  35. 62
  36. 65
  37. 90
  38. 26
  39. 12
  40. 57

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