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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 705 · 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 angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  2. 2.In triangle ABC, angle A = 22° and angle B = 94°. What is angle C (in degrees)?
  3. 3.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (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.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  7. 7.An exterior angle of a triangle is 63°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  8. 8.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 25° and 25°. What is the exterior angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  12. 12.Can a triangle have sides of 7 cm, 22 cm and 12 cm? (a) Yes (b) No
  13. 13.In triangle ABC, angle A = 83° and angle B = 27°. What is angle C (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  16. 16.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)?
  17. 17.In triangle ABC, angle A = 74° and angle B = 64°. What is angle C (in degrees)?
  18. 18.Can a triangle have sides of 8 cm, 25 cm and 12 cm? (a) No (b) Yes
  19. 19.Can a triangle have sides of 14 cm, 6 cm and 6 cm? (a) Yes (b) No
  20. 20.Can a triangle have sides of 8 cm, 8 cm and 8 cm? (a) Yes (b) No
  21. 21.In an isosceles triangle, the angle between the two equal sides is 76°. What is each of the other two angles (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 36° and 77°. What is the exterior angle (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 39° and angle B = 46°. What is angle C (in degrees)?
  25. 25.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)?
  26. 26.In triangle ABC, angle A = 46° and angle B = 58°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 88° and angle B = 32°. What is angle C (in degrees)?
  28. 28.In triangle ABC, angle A = 69° and angle B = 61°. What is angle C (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  30. 30.Can a triangle have sides of 10 cm, 17 cm and 10 cm? (a) Yes (b) No
  31. 31.In an isosceles triangle, the two equal angles are 55° each. What is the third angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  33. 33.Can a triangle have sides of 7 cm, 11 cm and 9 cm? (a) Yes (b) No
  34. 34.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  35. 35.In triangle ABC, angle A = 52° and angle B = 104°. What is angle C (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  37. 37.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  38. 38.In triangle ABC, angle A = 77° and angle B = 44°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 72° each. What is the third angle (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?

Answer key

  1. 50
  2. 64
  3. 72
  4. 77
  5. 32
  6. 32
  7. 26
  8. 36
  9. 61
  10. 50
  11. 40
  12. No
  13. 70
  14. 18
  15. 13
  16. 12
  17. 42
  18. No
  19. No
  20. Yes
  21. 52
  22. 113
  23. 82
  24. 95
  25. 7
  26. 76
  27. 60
  28. 50
  29. 134
  30. Yes
  31. 70
  32. 90
  33. Yes
  34. 15
  35. 24
  36. 26
  37. 8
  38. 59
  39. 36
  40. 26

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