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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 412 · 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.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  2. 2.Can a triangle have sides of 5 cm, 7 cm and 5 cm? (a) No (b) Yes
  3. 3.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  4. 4.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  5. 5.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)?
  6. 6.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 49° and angle B = 95°. What is angle C (in degrees)?
  10. 10.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  11. 11.Can a triangle have sides of 19 cm, 7 cm and 10 cm? (a) Yes (b) No
  12. 12.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  13. 13.Can a triangle have sides of 12 cm, 15 cm and 2 cm? (a) Yes (b) No
  14. 14.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  16. 16.In triangle ABC, angle A = 35° and angle B = 93°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 92° and angle B = 50°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 50° and angle B = 45°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  20. 20.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  21. 21.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  22. 22.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  24. 24.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  25. 25.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 44° and angle B = 104°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 10 cm, 14 cm and 3 cm? (a) No (b) Yes
  28. 28.An exterior angle of a triangle is 123°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  29. 29.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  30. 30.In triangle ABC, angle A = 26° and angle B = 63°. What is angle C (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  32. 32.In triangle ABC, angle A = 70° and angle B = 31°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 66° and angle B = 29°. What is angle C (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  36. 36.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  39. 39.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)?
  40. 40.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?

Answer key

  1. 42
  2. Yes
  3. 50
  4. 36
  5. 24
  6. 106
  7. 64
  8. 50
  9. 36
  10. 38
  11. No
  12. 48
  13. No
  14. 45
  15. 90
  16. 52
  17. 38
  18. 85
  19. 45
  20. 27
  21. 48
  22. 20
  23. 27
  24. 28
  25. 70
  26. 32
  27. No
  28. 56
  29. 18
  30. 91
  31. 120
  32. 79
  33. 85
  34. 37
  35. 72
  36. 45
  37. 60
  38. 54
  39. 10
  40. 34

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