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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 804 · 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.An exterior angle of a triangle is 133°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  3. 3.In an isosceles triangle, the two equal angles are 72° each. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 7 cm, 3 cm and 3 cm? (a) Yes (b) No
  5. 5.In triangle ABC, angle A = 60° and angle B = 98°. What is angle C (in degrees)?
  6. 6.Can a triangle have sides of 7 cm, 2 cm and 2 cm? (a) Yes (b) No
  7. 7.The two interior opposite angles of a triangle are 59° and 25°. What is the exterior angle (in degrees)?
  8. 8.In triangle ABC, angle A = 69° and angle B = 40°. What is angle C (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  10. 10.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  13. 13.Can a triangle have sides of 17 cm, 12 cm and 4 cm? (a) Yes (b) No
  14. 14.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  15. 15.Can a triangle have sides of 5 cm, 3 cm and 3 cm? (a) No (b) Yes
  16. 16.In triangle ABC, angle A = 43° and angle B = 82°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 100° and angle B = 54°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 39° and angle B = 67°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 44° and angle B = 87°. What is angle C (in degrees)?
  20. 20.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  21. 21.In triangle ABC, angle A = 20° and angle B = 41°. What is angle C (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 31° and 21°. What is the exterior angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 43° and 26°. What is the exterior angle (in degrees)?
  25. 25.Can a triangle have sides of 8 cm, 12 cm and 6 cm? (a) Yes (b) No
  26. 26.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  27. 27.Can a triangle have sides of 11 cm, 23 cm and 8 cm? (a) Yes (b) No
  28. 28.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  29. 29.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  31. 31.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  33. 33.Can a triangle have sides of 8 cm, 9 cm and 2 cm? (a) No (b) Yes
  34. 34.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 26° and angle B = 60°. What is angle C (in degrees)?
  36. 36.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  37. 37.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 45° and 67°. What is the exterior angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 28° and 26°. What is the exterior angle (in degrees)?

Answer key

  1. 79
  2. 17
  3. 36
  4. No
  5. 22
  6. No
  7. 84
  8. 71
  9. 14
  10. 40
  11. 90
  12. 40
  13. No
  14. 70
  15. Yes
  16. 55
  17. 26
  18. 74
  19. 49
  20. 28
  21. 119
  22. 52
  23. 75
  24. 69
  25. Yes
  26. 20
  27. No
  28. 3
  29. 100
  30. 25
  31. 75
  32. 48
  33. Yes
  34. 80
  35. 94
  36. 72
  37. 41
  38. 112
  39. 90
  40. 54

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