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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 261 · 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.In triangle ABC, angle A = 62° and angle B = 30°. What is angle C (in degrees)?
  2. 2.In triangle ABC, angle A = 21° and angle B = 125°. What is angle C (in degrees)?
  3. 3.In triangle ABC, angle A = 56° and angle B = 78°. What is angle C (in degrees)?
  4. 4.Can a triangle have sides of 2 cm, 10 cm and 10 cm? (a) No (b) Yes
  5. 5.In triangle ABC, angle A = 87° and angle B = 38°. What is angle C (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 32° and 28°. What is the exterior angle (in degrees)?
  7. 7.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  9. 9.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 66° and angle B = 83°. What is angle C (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 28° and 51°. What is the exterior angle (in degrees)?
  12. 12.In triangle ABC, angle A = 42° and angle B = 111°. What is angle C (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  15. 15.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  16. 16.Can a triangle have sides of 1 cm, 6 cm and 6 cm? (a) No (b) Yes
  17. 17.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  18. 18.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)?
  19. 19.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 21° and 20°. What is the exterior angle (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 57° and angle B = 71°. What is angle C (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  28. 28.The two interior opposite angles of a triangle are 53° and 77°. What is the exterior angle (in degrees)?
  29. 29.In triangle ABC, angle A = 42° and angle B = 55°. What is angle C (in degrees)?
  30. 30.An exterior angle of a triangle is 127°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  32. 32.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  33. 33.The two interior opposite angles of a triangle are 47° and 49°. What is the exterior angle (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  36. 36.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  38. 38.Can a triangle have sides of 23 cm, 8 cm and 12 cm? (a) No (b) Yes
  39. 39.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  40. 40.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)?

Answer key

  1. 88
  2. 34
  3. 46
  4. Yes
  5. 55
  6. 60
  7. 58
  8. 25
  9. 24
  10. 31
  11. 79
  12. 27
  13. 120
  14. 12
  15. 16
  16. Yes
  17. 60
  18. 12
  19. 43
  20. 80
  21. 41
  22. 88
  23. 100
  24. 56
  25. 36
  26. 52
  27. 30
  28. 130
  29. 83
  30. 50
  31. 70
  32. 9
  33. 96
  34. 10
  35. 13
  36. 100
  37. 69
  38. No
  39. 72
  40. 7

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