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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 964 · 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 a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  2. 2.In triangle ABC, angle A = 61° and angle B = 29°. What is angle C (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 36° and angle B = 102°. What is angle C (in degrees)?
  5. 5.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  9. 9.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  10. 10.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  11. 11.Can a triangle have sides of 19 cm, 8 cm and 11 cm? (a) Yes (b) No
  12. 12.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  14. 14.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)?
  15. 15.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  16. 16.Can a triangle have sides of 10 cm, 10 cm and 13 cm? (a) Yes (b) No
  17. 17.The two interior opposite angles of a triangle are 75° and 48°. What is the exterior angle (in degrees)?
  18. 18.Can a triangle have sides of 18 cm, 7 cm and 7 cm? (a) Yes (b) No
  19. 19.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  20. 20.In triangle ABC, angle A = 78° and angle B = 61°. What is angle C (in degrees)?
  21. 21.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  22. 22.Can a triangle have sides of 7 cm, 7 cm and 2 cm? (a) No (b) Yes
  23. 23.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  24. 24.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  25. 25.In triangle ABC, angle A = 91° and angle B = 57°. What is angle C (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  27. 27.In triangle ABC, angle A = 70° and angle B = 20°. What is angle C (in degrees)?
  28. 28.In triangle ABC, angle A = 95° and angle B = 30°. What is angle C (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  30. 30.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  31. 31.Can a triangle have sides of 14 cm, 9 cm and 12 cm? (a) No (b) Yes
  32. 32.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)?
  33. 33.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 97° and angle B = 50°. What is angle C (in degrees)?
  35. 35.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)?
  36. 36.Can a triangle have sides of 3 cm, 13 cm and 6 cm? (a) No (b) Yes
  37. 37.Can a triangle have sides of 3 cm, 10 cm and 5 cm? (a) Yes (b) No
  38. 38.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  39. 39.In triangle ABC, angle A = 41° and angle B = 31°. What is angle C (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?

Answer key

  1. 76
  2. 90
  3. 78
  4. 42
  5. 48
  6. 74
  7. 57
  8. 25
  9. 90
  10. 77
  11. No
  12. 18
  13. 13
  14. 5
  15. 43
  16. Yes
  17. 123
  18. No
  19. 20
  20. 41
  21. 65
  22. Yes
  23. 36
  24. 46
  25. 32
  26. 40
  27. 90
  28. 55
  29. 35
  30. 37
  31. Yes
  32. 8
  33. 79
  34. 33
  35. 3
  36. No
  37. No
  38. 67
  39. 108
  40. 71

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