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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 203 · 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 8 cm, 3 cm and 7 cm? (a) No (b) Yes
  2. 2.Can a triangle have sides of 12 cm, 5 cm and 8 cm? (a) Yes (b) No
  3. 3.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  6. 6.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  7. 7.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  11. 11.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  15. 15.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)?
  16. 16.Can a triangle have sides of 5 cm, 2 cm and 4 cm? (a) Yes (b) No
  17. 17.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  18. 18.Can a triangle have sides of 4 cm, 5 cm and 7 cm? (a) Yes (b) No
  19. 19.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  20. 20.The two interior opposite angles of a triangle are 32° and 61°. What is the exterior angle (in degrees)?
  21. 21.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  22. 22.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  23. 23.In triangle ABC, angle A = 49° and angle B = 29°. What is angle C (in degrees)?
  24. 24.Can a triangle have sides of 25 cm, 10 cm and 12 cm? (a) No (b) Yes
  25. 25.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 10 cm, 19 cm and 8 cm? (a) Yes (b) No
  27. 27.Can a triangle have sides of 19 cm, 7 cm and 11 cm? (a) No (b) Yes
  28. 28.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  29. 29.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)?
  30. 30.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  31. 31.In triangle ABC, angle A = 36° and angle B = 37°. What is angle C (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  33. 33.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  34. 34.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  36. 36.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  39. 39.An exterior angle of a triangle is 53°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?

Answer key

  1. Yes
  2. Yes
  3. 84
  4. 72
  5. 94
  6. 5
  7. 53
  8. 90
  9. 54
  10. 15
  11. 49
  12. 100
  13. 90
  14. 39
  15. 15
  16. Yes
  17. 51
  18. Yes
  19. 25
  20. 93
  21. 33
  22. 39
  23. 102
  24. No
  25. 42
  26. No
  27. No
  28. 36
  29. 7
  30. 72
  31. 107
  32. 77
  33. 36
  34. 42
  35. 39
  36. 50
  37. 45
  38. 25
  39. 27
  40. 13

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