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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 122 · 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 29°. What is the third angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 44° and 54°. What is the exterior angle (in degrees)?
  3. 3.Can a triangle have sides of 11 cm, 10 cm and 7 cm? (a) Yes (b) No
  4. 4.In triangle ABC, angle A = 45° and angle B = 62°. What is angle C (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  7. 7.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  8. 8.An exterior angle of a triangle is 145°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  9. 9.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  10. 10.Can a triangle have sides of 4 cm, 13 cm and 9 cm? (a) No (b) Yes
  11. 11.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  13. 13.Can a triangle have sides of 9 cm, 21 cm and 10 cm? (a) No (b) Yes
  14. 14.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 62° each. What is the third angle (in degrees)?
  17. 17.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  18. 18.Can a triangle have sides of 8 cm, 6 cm and 15 cm? (a) No (b) Yes
  19. 19.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 66° and 33°. What is the exterior angle (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  22. 22.In triangle ABC, angle A = 69° and angle B = 45°. What is angle C (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 48° and 29°. What is the exterior angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  26. 26.In triangle ABC, angle A = 20° and angle B = 125°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 6 cm, 16 cm and 7 cm? (a) No (b) Yes
  28. 28.In triangle ABC, angle A = 68° and angle B = 25°. What is angle C (in degrees)?
  29. 29.Can a triangle have sides of 9 cm, 23 cm and 9 cm? (a) Yes (b) No
  30. 30.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  32. 32.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  33. 33.Can a triangle have sides of 7 cm, 9 cm and 4 cm? (a) No (b) Yes
  34. 34.Can a triangle have sides of 13 cm, 6 cm and 7 cm? (a) No (b) Yes
  35. 35.An exterior angle of a triangle is 137°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  37. 37.Can a triangle have sides of 7 cm, 8 cm and 12 cm? (a) No (b) Yes
  38. 38.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  39. 39.In triangle ABC, angle A = 32° and angle B = 73°. What is angle C (in degrees)?
  40. 40.An exterior angle of a triangle is 132°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?

Answer key

  1. 61
  2. 98
  3. Yes
  4. 73
  5. 77
  6. 62
  7. 70
  8. 75
  9. 4
  10. No
  11. 132
  12. 36
  13. No
  14. 67
  15. 76
  16. 56
  17. 24
  18. No
  19. 55
  20. 99
  21. 17
  22. 66
  23. 77
  24. 17
  25. 62
  26. 35
  27. No
  28. 87
  29. No
  30. 42
  31. 63
  32. 54
  33. Yes
  34. No
  35. 62
  36. 13
  37. Yes
  38. 34
  39. 75
  40. 66

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