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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 621 · 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, 10 cm and 9 cm? (a) Yes (b) No
  2. 2.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  4. 4.In triangle ABC, angle A = 50° and angle B = 70°. What is angle C (in degrees)?
  5. 5.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 8 cm, 2 cm and 14 cm? (a) Yes (b) No
  9. 9.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  10. 10.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  11. 11.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)?
  12. 12.In triangle ABC, angle A = 27° and angle B = 40°. What is angle C (in degrees)?
  13. 13.Can a triangle have sides of 8 cm, 11 cm and 11 cm? (a) No (b) Yes
  14. 14.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  16. 16.Can a triangle have sides of 4 cm, 12 cm and 19 cm? (a) Yes (b) No
  17. 17.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 3 cm, 18 cm and 11 cm? (a) Yes (b) No
  19. 19.Can a triangle have sides of 11 cm, 10 cm and 26 cm? (a) Yes (b) No
  20. 20.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  21. 21.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  22. 22.In triangle ABC, angle A = 22° and angle B = 26°. What is angle C (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  25. 25.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)?
  26. 26.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  27. 27.Can a triangle have sides of 23 cm, 7 cm and 12 cm? (a) No (b) Yes
  28. 28.The two interior opposite angles of a triangle are 67° and 30°. What is the exterior angle (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 70° and angle B = 86°. What is angle C (in degrees)?
  31. 31.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  32. 32.Can a triangle have sides of 9 cm, 1 cm and 9 cm? (a) Yes (b) No
  33. 33.In triangle ABC, angle A = 89° and angle B = 67°. What is angle C (in degrees)?
  34. 34.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  36. 36.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  37. 37.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  38. 38.Can a triangle have sides of 12 cm, 8 cm and 21 cm? (a) Yes (b) No
  39. 39.The two interior opposite angles of a triangle are 21° and 79°. What is the exterior angle (in degrees)?
  40. 40.In triangle ABC, angle A = 100° and angle B = 30°. What is angle C (in degrees)?

Answer key

  1. Yes
  2. 21
  3. 90
  4. 60
  5. 31
  6. 55
  7. 71
  8. No
  9. 39
  10. 46
  11. 24
  12. 113
  13. Yes
  14. 75
  15. 90
  16. No
  17. 25
  18. No
  19. No
  20. 74
  21. 45
  22. 132
  23. 63
  24. 55
  25. 6
  26. 20
  27. No
  28. 97
  29. 98
  30. 24
  31. 25
  32. Yes
  33. 24
  34. 46
  35. 10
  36. 8
  37. 69
  38. No
  39. 100
  40. 50

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