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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 981 · 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.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  2. 2.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  3. 3.Can a triangle have sides of 11 cm, 6 cm and 5 cm? (a) Yes (b) No
  4. 4.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 34° and 24°. What is the exterior angle (in degrees)?
  6. 6.Can a triangle have sides of 22 cm, 8 cm and 10 cm? (a) No (b) Yes
  7. 7.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  8. 8.In triangle ABC, angle A = 36° and angle B = 67°. What is angle C (in degrees)?
  9. 9.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  10. 10.In triangle ABC, angle A = 55° and angle B = 30°. What is angle C (in degrees)?
  11. 11.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  12. 12.Can a triangle have sides of 14 cm, 6 cm and 8 cm? (a) No (b) Yes
  13. 13.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  14. 14.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  15. 15.In triangle ABC, angle A = 50° and angle B = 108°. What is angle C (in degrees)?
  16. 16.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)?
  17. 17.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 44° and angle B = 54°. What is angle C (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 72° and 34°. What is the exterior angle (in degrees)?
  20. 20.Can a triangle have sides of 2 cm, 7 cm and 7 cm? (a) Yes (b) No
  21. 21.In triangle ABC, angle A = 25° and angle B = 104°. What is angle C (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 79° and 43°. What is the exterior angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 30° and 77°. What is the exterior angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  25. 25.Can a triangle have sides of 7 cm, 10 cm and 19 cm? (a) No (b) Yes
  26. 26.In an isosceles triangle, the angle between the two equal sides is 96°. What is each of the other two angles (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  28. 28.Can a triangle have sides of 11 cm, 25 cm and 9 cm? (a) Yes (b) No
  29. 29.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles (in degrees)?
  30. 30.Can a triangle have sides of 17 cm, 9 cm and 3 cm? (a) Yes (b) No
  31. 31.Can a triangle have sides of 12 cm, 9 cm and 16 cm? (a) No (b) Yes
  32. 32.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 63° each. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 69° and 32°. What is the exterior angle (in degrees)?
  37. 37.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 39° and 46°. What is the exterior angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?

Answer key

  1. 7
  2. 24
  3. No
  4. 62
  5. 58
  6. No
  7. 69
  8. 77
  9. 50
  10. 95
  11. 60
  12. No
  13. 39
  14. 54
  15. 22
  16. 3
  17. 65
  18. 82
  19. 106
  20. Yes
  21. 51
  22. 122
  23. 107
  24. 20
  25. No
  26. 42
  27. 24
  28. No
  29. 30
  30. No
  31. Yes
  32. 64
  33. 27
  34. 54
  35. 10
  36. 101
  37. 73
  38. 85
  39. 55
  40. 70

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