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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 226 · 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.

NameDateTime takenScore ___ / 40
  1. 1.Can a triangle have sides of 23 cm, 9 cm and 11 cm? (a) Yes (b) No
  2. 2.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  5. 5.In triangle ABC, angle A = 72° and angle B = 24°. What is angle C (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 67° and 29°. What is the exterior angle (in degrees)?
  7. 7.In triangle ABC, angle A = 95° and angle B = 44°. What is angle C (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 60° and 72°. What is the exterior angle (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  11. 11.In triangle ABC, angle A = 100° and angle B = 53°. What is angle C (in degrees)?
  12. 12.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  14. 14.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  15. 15.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  16. 16.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  17. 17.In triangle ABC, angle A = 24° and angle B = 26°. What is angle C (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  19. 19.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 28° and angle B = 69°. What is angle C (in degrees)?
  24. 24.In triangle ABC, angle A = 81° and angle B = 64°. What is angle C (in degrees)?
  25. 25.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  26. 26.An exterior angle of a triangle is 134°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?
  28. 28.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  29. 29.Can a triangle have sides of 2 cm, 7 cm and 6 cm? (a) No (b) Yes
  30. 30.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)?
  31. 31.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  33. 33.Can a triangle have sides of 7 cm, 8 cm and 9 cm? (a) No (b) Yes
  34. 34.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?

Answer key

  1. No
  2. 20
  3. 106
  4. 80
  5. 84
  6. 96
  7. 41
  8. 132
  9. 74
  10. 120
  11. 27
  12. 54
  13. 10
  14. 24
  15. 37
  16. 24
  17. 130
  18. 90
  19. 15
  20. 29
  21. 20
  22. 48
  23. 83
  24. 35
  25. 31
  26. 60
  27. 38
  28. 70
  29. Yes
  30. 7
  31. 42
  32. 22
  33. Yes
  34. 38
  35. 72
  36. 116
  37. 18
  38. 40
  39. 90
  40. 17

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