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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 725 · 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 6 cm, 12 cm and 21 cm? (a) Yes (b) No
  2. 2.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  6. 6.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  7. 7.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  9. 9.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  12. 12.In triangle ABC, angle A = 34° and angle B = 38°. What is angle C (in degrees)?
  13. 13.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 60° and 27°. What is the exterior angle (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  18. 18.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  19. 19.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  21. 21.An exterior angle of a triangle is 62°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  22. 22.Can a triangle have sides of 5 cm, 3 cm and 11 cm? (a) Yes (b) No
  23. 23.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  24. 24.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  25. 25.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)?
  26. 26.In triangle ABC, angle A = 35° and angle B = 59°. What is angle C (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  28. 28.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 28° and 46°. What is the exterior angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 66° and 58°. What is the exterior angle (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  32. 32.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  33. 33.Can a triangle have sides of 6 cm, 3 cm and 14 cm? (a) No (b) Yes
  34. 34.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  36. 36.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  37. 37.Can a triangle have sides of 11 cm, 2 cm and 9 cm? (a) No (b) Yes
  38. 38.The two interior opposite angles of a triangle are 66° and 41°. What is the exterior angle (in degrees)?
  39. 39.In triangle ABC, angle A = 86° and angle B = 54°. What is angle C (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?

Answer key

  1. No
  2. 55
  3. 16
  4. 36
  5. 13
  6. 17
  7. 72
  8. 48
  9. 75
  10. 67
  11. 72
  12. 108
  13. 70
  14. 33
  15. 79
  16. 87
  17. 10
  18. 39
  19. 59
  20. 20
  21. 37
  22. No
  23. 48
  24. 62
  25. 10
  26. 86
  27. 39
  28. 66
  29. 74
  30. 124
  31. 25
  32. 90
  33. No
  34. 118
  35. 59
  36. 45
  37. No
  38. 107
  39. 40
  40. 60

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