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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 737 · 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 angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  2. 2.Can a triangle have sides of 12 cm, 19 cm and 6 cm? (a) No (b) Yes
  3. 3.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  4. 4.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  5. 5.In triangle ABC, angle A = 59° and angle B = 71°. What is angle C (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  7. 7.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)?
  8. 8.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 94° and angle B = 25°. What is angle C (in degrees)?
  10. 10.In triangle ABC, angle A = 63° and angle B = 59°. What is angle C (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 72° and 63°. What is the exterior angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 35° and 21°. What is the exterior angle (in degrees)?
  15. 15.In triangle ABC, angle A = 44° and angle B = 20°. What is angle C (in degrees)?
  16. 16.An exterior angle of a triangle is 45°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  17. 17.In triangle ABC, angle A = 72° and angle B = 21°. What is angle C (in degrees)?
  18. 18.Can a triangle have sides of 3 cm, 5 cm and 4 cm? (a) Yes (b) No
  19. 19.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)?
  20. 20.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 99° and angle B = 46°. What is angle C (in degrees)?
  22. 22.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)?
  23. 23.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 56° and 65°. What is the exterior angle (in degrees)?
  25. 25.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  26. 26.In triangle ABC, angle A = 48° and angle B = 104°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 10 cm, 19 cm and 10 cm? (a) No (b) Yes
  28. 28.Can a triangle have sides of 9 cm, 11 cm and 4 cm? (a) Yes (b) No
  29. 29.In triangle ABC, angle A = 24° and angle B = 41°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 88° and angle B = 55°. What is angle C (in degrees)?
  31. 31.Can a triangle have sides of 13 cm, 12 cm and 3 cm? (a) No (b) Yes
  32. 32.In triangle ABC, angle A = 49° and angle B = 100°. What is angle C (in degrees)?
  33. 33.An exterior angle of a triangle is 120°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 40° and angle B = 102°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 22° and angle B = 52°. What is angle C (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 20 cm, 10 cm and 10 cm? (a) Yes (b) No
  39. 39.In triangle ABC, angle A = 74° and angle B = 29°. What is angle C (in degrees)?
  40. 40.Can a triangle have sides of 11 cm, 18 cm and 7 cm? (a) No (b) Yes

Answer key

  1. 75
  2. No
  3. 10
  4. 22
  5. 50
  6. 108
  7. 24
  8. 100
  9. 61
  10. 58
  11. 23
  12. 128
  13. 135
  14. 56
  15. 116
  16. 21
  17. 87
  18. Yes
  19. 10
  20. 60
  21. 35
  22. 15
  23. 36
  24. 121
  25. 27
  26. 28
  27. Yes
  28. Yes
  29. 115
  30. 37
  31. Yes
  32. 31
  33. 40
  34. 24
  35. 38
  36. 106
  37. 33
  38. No
  39. 77
  40. No

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