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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 901 · 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 = 54° and angle B = 46°. What is angle C (in degrees)?
  2. 2.Can a triangle have sides of 2 cm, 8 cm and 10 cm? (a) Yes (b) No
  3. 3.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  5. 5.In triangle ABC, angle A = 70° and angle B = 49°. What is angle C (in degrees)?
  6. 6.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  7. 7.An exterior angle of a triangle is 135°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  9. 9.Can a triangle have sides of 7 cm, 5 cm and 3 cm? (a) Yes (b) No
  10. 10.An exterior angle of a triangle is 62°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  12. 12.In triangle ABC, angle A = 69° and angle B = 80°. What is angle C (in degrees)?
  13. 13.Can a triangle have sides of 3 cm, 10 cm and 9 cm? (a) Yes (b) No
  14. 14.An exterior angle of a triangle is 121°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 56° and 45°. What is the exterior angle (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 4 cm, 6 cm and 10 cm? (a) No (b) Yes
  19. 19.The two interior opposite angles of a triangle are 65° and 36°. What is the exterior angle (in degrees)?
  20. 20.Can a triangle have sides of 10 cm, 9 cm and 9 cm? (a) Yes (b) No
  21. 21.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 80° and angle B = 56°. What is angle C (in degrees)?
  23. 23.An exterior angle of a triangle is 54°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  24. 24.In triangle ABC, angle A = 23° and angle B = 65°. What is angle C (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  26. 26.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 82° and angle B = 56°. What is angle C (in degrees)?
  28. 28.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 63° each. What is the third angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 41° and 38°. What is the exterior angle (in degrees)?
  31. 31.Can a triangle have sides of 3 cm, 7 cm and 6 cm? (a) No (b) Yes
  32. 32.Can a triangle have sides of 7 cm, 8 cm and 20 cm? (a) Yes (b) No
  33. 33.In triangle ABC, angle A = 55° and angle B = 29°. What is angle C (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  35. 35.Can a triangle have sides of 2 cm, 7 cm and 2 cm? (a) No (b) Yes
  36. 36.Can a triangle have sides of 7 cm, 3 cm and 3 cm? (a) Yes (b) No
  37. 37.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?

Answer key

  1. 80
  2. No
  3. 45
  4. 29
  5. 61
  6. 22
  7. 59
  8. 90
  9. Yes
  10. 34
  11. 70
  12. 31
  13. Yes
  14. 69
  15. 101
  16. 120
  17. 10
  18. No
  19. 101
  20. Yes
  21. 72
  22. 44
  23. 28
  24. 92
  25. 13
  26. 31
  27. 42
  28. 21
  29. 54
  30. 79
  31. Yes
  32. No
  33. 96
  34. 47
  35. No
  36. No
  37. 11
  38. 51
  39. 74
  40. 20

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