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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 28 · 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 1 : 1 : 2. What is the smallest angle (in degrees)?
  2. 2.In triangle ABC, angle A = 99° and angle B = 34°. What is angle C (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 87° and angle B = 69°. What is angle C (in degrees)?
  5. 5.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 53° and angle B = 23°. What is angle C (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  12. 12.Can a triangle have sides of 3 cm, 19 cm and 12 cm? (a) No (b) Yes
  13. 13.The two interior opposite angles of a triangle are 46° and 48°. What is the exterior angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 30° and 51°. What is the exterior angle (in degrees)?
  15. 15.In triangle ABC, angle A = 53° and angle B = 28°. What is angle C (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  17. 17.In triangle ABC, angle A = 48° and angle B = 31°. What is angle C (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  19. 19.Can a triangle have sides of 4 cm, 4 cm and 11 cm? (a) Yes (b) No
  20. 20.In triangle ABC, angle A = 66° and angle B = 75°. What is angle C (in degrees)?
  21. 21.An exterior angle of a triangle is 64°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  24. 24.Can a triangle have sides of 9 cm, 2 cm and 11 cm? (a) Yes (b) No
  25. 25.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  26. 26.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  27. 27.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  28. 28.In triangle ABC, angle A = 25° and angle B = 105°. What is angle C (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 41° and 73°. What is the exterior angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 30° and 22°. What is the exterior angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  33. 33.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  35. 35.In triangle ABC, angle A = 45° and angle B = 87°. What is angle C (in degrees)?
  36. 36.Can a triangle have sides of 11 cm, 2 cm and 15 cm? (a) Yes (b) No
  37. 37.Can a triangle have sides of 4 cm, 9 cm and 12 cm? (a) Yes (b) No
  38. 38.In triangle ABC, angle A = 23° and angle B = 30°. What is angle C (in degrees)?
  39. 39.Can a triangle have sides of 10 cm, 10 cm and 15 cm? (a) No (b) Yes
  40. 40.In triangle ABC, angle A = 20° and angle B = 136°. What is angle C (in degrees)?

Answer key

  1. 45
  2. 47
  3. 22
  4. 24
  5. 45
  6. 72
  7. 27
  8. 90
  9. 104
  10. 18
  11. 14
  12. No
  13. 94
  14. 81
  15. 99
  16. 77
  17. 101
  18. 50
  19. No
  20. 39
  21. 35
  22. 90
  23. 36
  24. No
  25. 17
  26. 25
  27. 50
  28. 50
  29. 114
  30. 52
  31. 29
  32. 75
  33. 52
  34. 20
  35. 48
  36. No
  37. Yes
  38. 127
  39. Yes
  40. 24

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