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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 660 · 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 5 cm, 5 cm and 13 cm? (a) Yes (b) No
  2. 2.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  3. 3.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)?
  4. 4.In triangle ABC, angle A = 57° and angle B = 93°. What is angle C (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  7. 7.Can a triangle have sides of 2 cm, 11 cm and 13 cm? (a) Yes (b) No
  8. 8.Can a triangle have sides of 9 cm, 4 cm and 10 cm? (a) Yes (b) No
  9. 9.Can a triangle have sides of 6 cm, 11 cm and 10 cm? (a) Yes (b) No
  10. 10.In an isosceles triangle, the angle between the two equal sides is 154°. What is each of the other two angles (in degrees)?
  11. 11.Can a triangle have sides of 11 cm, 6 cm and 16 cm? (a) No (b) Yes
  12. 12.In triangle ABC, angle A = 79° and angle B = 20°. What is angle C (in degrees)?
  13. 13.In triangle ABC, angle A = 48° and angle B = 40°. What is angle C (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  15. 15.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)?
  16. 16.In triangle ABC, angle A = 31° and angle B = 119°. What is angle C (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  18. 18.In triangle ABC, angle A = 64° and angle B = 78°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  20. 20.Can a triangle have sides of 14 cm, 7 cm and 4 cm? (a) Yes (b) No
  21. 21.In triangle ABC, angle A = 76° and angle B = 66°. What is angle C (in degrees)?
  22. 22.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  23. 23.In triangle ABC, angle A = 77° and angle B = 73°. What is angle C (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  27. 27.In triangle ABC, angle A = 71° and angle B = 73°. What is angle C (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 31° and 29°. What is the exterior angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  30. 30.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  31. 31.In triangle ABC, angle A = 90° and angle B = 58°. What is angle C (in degrees)?
  32. 32.Can a triangle have sides of 8 cm, 6 cm and 18 cm? (a) Yes (b) No
  33. 33.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 39° and 58°. What is the exterior angle (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  38. 38.In triangle ABC, angle A = 79° and angle B = 45°. What is angle C (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  40. 40.An exterior angle of a triangle is 121°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?

Answer key

  1. No
  2. 65
  3. 8
  4. 30
  5. 19
  6. 70
  7. No
  8. Yes
  9. Yes
  10. 13
  11. Yes
  12. 81
  13. 92
  14. 72
  15. 24
  16. 30
  17. 90
  18. 38
  19. 72
  20. No
  21. 38
  22. 59
  23. 30
  24. 16
  25. 32
  26. 39
  27. 36
  28. 60
  29. 54
  30. 38
  31. 32
  32. No
  33. 90
  34. 12
  35. 18
  36. 97
  37. 26
  38. 56
  39. 13
  40. 76

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