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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 689 · 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 = 31° and angle B = 88°. What is angle C (in degrees)?
  2. 2.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)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  5. 5.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 66° and angle B = 65°. What is angle C (in degrees)?
  8. 8.Can a triangle have sides of 2 cm, 2 cm and 5 cm? (a) Yes (b) No
  9. 9.Can a triangle have sides of 11 cm, 12 cm and 6 cm? (a) Yes (b) No
  10. 10.The two interior opposite angles of a triangle are 37° and 79°. What is the exterior angle (in degrees)?
  11. 11.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  12. 12.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 64°. What is each of the other two angles (in degrees)?
  16. 16.Can a triangle have sides of 8 cm, 6 cm and 12 cm? (a) No (b) Yes
  17. 17.In triangle ABC, angle A = 27° and angle B = 127°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 61° and angle B = 43°. What is angle C (in degrees)?
  19. 19.Can a triangle have sides of 6 cm, 10 cm and 9 cm? (a) No (b) Yes
  20. 20.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  24. 24.Can a triangle have sides of 5 cm, 6 cm and 2 cm? (a) No (b) Yes
  25. 25.The two interior opposite angles of a triangle are 58° and 30°. What is the exterior angle (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 47° and 73°. What is the exterior angle (in degrees)?
  27. 27.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)?
  28. 28.In triangle ABC, angle A = 56° and angle B = 55°. What is angle C (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  30. 30.In triangle ABC, angle A = 79° and angle B = 29°. What is angle C (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  32. 32.Can a triangle have sides of 4 cm, 2 cm and 3 cm? (a) No (b) Yes
  33. 33.In triangle ABC, angle A = 53° and angle B = 91°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 35° and angle B = 38°. What is angle C (in degrees)?
  35. 35.In triangle ABC, angle A = 99° and angle B = 26°. What is angle C (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 50° and 55°. What is the exterior angle (in degrees)?
  37. 37.Can a triangle have sides of 9 cm, 18 cm and 9 cm? (a) No (b) Yes
  38. 38.Can a triangle have sides of 7 cm, 7 cm and 2 cm? (a) No (b) Yes
  39. 39.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?

Answer key

  1. 61
  2. 12
  3. 71
  4. 77
  5. 90
  6. 63
  7. 49
  8. No
  9. Yes
  10. 116
  11. 23
  12. 24
  13. 15
  14. 36
  15. 58
  16. Yes
  17. 26
  18. 76
  19. Yes
  20. 18
  21. 124
  22. 48
  23. 26
  24. Yes
  25. 88
  26. 120
  27. 8
  28. 69
  29. 25
  30. 72
  31. 75
  32. Yes
  33. 36
  34. 107
  35. 55
  36. 105
  37. No
  38. Yes
  39. 82
  40. 54

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