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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 732 · 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.The two interior opposite angles of a triangle are 56° and 78°. What is the exterior angle (in degrees)?
  2. 2.Can a triangle have sides of 4 cm, 5 cm and 6 cm? (a) No (b) Yes
  3. 3.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)?
  4. 4.Can a triangle have sides of 2 cm, 8 cm and 8 cm? (a) No (b) Yes
  5. 5.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 2 cm, 11 cm and 10 cm? (a) Yes (b) No
  7. 7.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  8. 8.In triangle ABC, angle A = 62° and angle B = 62°. What is angle C (in degrees)?
  9. 9.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  10. 10.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)?
  11. 11.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  12. 12.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  15. 15.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  18. 18.The two interior opposite angles of a triangle are 22° and 30°. What is the exterior angle (in degrees)?
  19. 19.In triangle ABC, angle A = 95° and angle B = 56°. What is angle C (in degrees)?
  20. 20.In triangle ABC, angle A = 23° and angle B = 109°. What is angle C (in degrees)?
  21. 21.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  22. 22.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 25° and angle B = 104°. What is angle C (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 94°. What is each of the other two angles (in degrees)?
  26. 26.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  27. 27.The two interior opposite angles of a triangle are 35° and 24°. What is the exterior angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 33° and 49°. What is the exterior angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 55° and 77°. What is the exterior angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  33. 33.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 64° and 22°. What is the exterior angle (in degrees)?
  35. 35.Can a triangle have sides of 4 cm, 9 cm and 4 cm? (a) No (b) Yes
  36. 36.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  37. 37.In triangle ABC, angle A = 40° and angle B = 64°. What is angle C (in degrees)?
  38. 38.In triangle ABC, angle A = 43° and angle B = 45°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  40. 40.In triangle ABC, angle A = 51° and angle B = 61°. What is angle C (in degrees)?

Answer key

  1. 134
  2. Yes
  3. 4
  4. Yes
  5. 37
  6. Yes
  7. 25
  8. 56
  9. 90
  10. 7
  11. 10
  12. 30
  13. 45
  14. 5
  15. 90
  16. 73
  17. 13
  18. 52
  19. 29
  20. 48
  21. 6
  22. 23
  23. 51
  24. 56
  25. 43
  26. 15
  27. 59
  28. 72
  29. 82
  30. 132
  31. 57
  32. 25
  33. 10
  34. 86
  35. No
  36. 30
  37. 76
  38. 92
  39. 60
  40. 68

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