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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 212 · 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.In triangle ABC, angle A = 68° and angle B = 49°. What is angle C (in degrees)?
  2. 2.Can a triangle have sides of 11 cm, 4 cm and 7 cm? (a) No (b) Yes
  3. 3.In triangle ABC, angle A = 53° and angle B = 32°. What is angle C (in degrees)?
  4. 4.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  6. 6.In triangle ABC, angle A = 57° and angle B = 82°. What is angle C (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 61° and 26°. What is the exterior angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 47° and 67°. What is the exterior angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 31° and angle B = 37°. What is angle C (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  13. 13.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  14. 14.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)?
  15. 15.Can a triangle have sides of 8 cm, 18 cm and 9 cm? (a) Yes (b) No
  16. 16.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  17. 17.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  18. 18.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  19. 19.The two interior opposite angles of a triangle are 43° and 43°. What is the exterior angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  21. 21.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  22. 22.The two interior opposite angles of a triangle are 59° and 41°. What is the exterior angle (in degrees)?
  23. 23.In triangle ABC, angle A = 79° and angle B = 71°. What is angle C (in degrees)?
  24. 24.Can a triangle have sides of 17 cm, 11 cm and 4 cm? (a) Yes (b) No
  25. 25.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 23° and angle B = 29°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 7 cm, 4 cm and 4 cm? (a) No (b) Yes
  28. 28.The two interior opposite angles of a triangle are 28° and 78°. What is the exterior angle (in degrees)?
  29. 29.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)?
  30. 30.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  31. 31.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  33. 33.Can a triangle have sides of 19 cm, 8 cm and 8 cm? (a) No (b) Yes
  34. 34.In an isosceles triangle, the two equal angles are 61° each. What is the third angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  38. 38.Can a triangle have sides of 11 cm, 8 cm and 4 cm? (a) No (b) Yes
  39. 39.Can a triangle have sides of 8 cm, 2 cm and 9 cm? (a) No (b) Yes
  40. 40.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?

Answer key

  1. 63
  2. No
  3. 95
  4. 59
  5. 72
  6. 41
  7. 87
  8. 114
  9. 45
  10. 62
  11. 112
  12. 80
  13. 15
  14. 15
  15. No
  16. 8
  17. 65
  18. 5
  19. 86
  20. 33
  21. 8
  22. 100
  23. 30
  24. No
  25. 38
  26. 128
  27. Yes
  28. 106
  29. 24
  30. 45
  31. 6
  32. 17
  33. No
  34. 58
  35. 90
  36. 53
  37. 25
  38. Yes
  39. Yes
  40. 54

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