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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 829 · 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.

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  1. 1.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  3. 3.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 52° and 67°. What is the exterior angle (in degrees)?
  7. 7.In triangle ABC, angle A = 33° and angle B = 38°. What is angle C (in degrees)?
  8. 8.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)?
  9. 9.Can a triangle have sides of 10 cm, 9 cm and 3 cm? (a) No (b) Yes
  10. 10.The two interior opposite angles of a triangle are 43° and 39°. What is the exterior angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  12. 12.Can a triangle have sides of 7 cm, 7 cm and 9 cm? (a) Yes (b) No
  13. 13.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  14. 14.In triangle ABC, angle A = 54° and angle B = 90°. What is angle C (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  16. 16.In triangle ABC, angle A = 80° and angle B = 65°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 43° and 80°. What is the exterior angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  21. 21.In triangle ABC, angle A = 65° and angle B = 26°. What is angle C (in degrees)?
  22. 22.Can a triangle have sides of 6 cm, 20 cm and 11 cm? (a) Yes (b) No
  23. 23.The two interior opposite angles of a triangle are 53° and 59°. What is the exterior angle (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 46° and 71°. What is the exterior angle (in degrees)?
  25. 25.In triangle ABC, angle A = 56° and angle B = 78°. What is angle C (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  27. 27.Can a triangle have sides of 8 cm, 10 cm and 11 cm? (a) Yes (b) No
  28. 28.Can a triangle have sides of 10 cm, 23 cm and 12 cm? (a) Yes (b) No
  29. 29.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  31. 31.Can a triangle have sides of 4 cm, 11 cm and 8 cm? (a) No (b) Yes
  32. 32.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  33. 33.In triangle ABC, angle A = 49° and angle B = 38°. What is angle C (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  35. 35.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  37. 37.An exterior angle of a triangle is 129°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 26° and 48°. What is the exterior angle (in degrees)?

Answer key

  1. 36
  2. 17
  3. 80
  4. 40
  5. 140
  6. 119
  7. 109
  8. 15
  9. Yes
  10. 82
  11. 84
  12. Yes
  13. 29
  14. 36
  15. 27
  16. 35
  17. 73
  18. 20
  19. 123
  20. 71
  21. 89
  22. No
  23. 112
  24. 117
  25. 46
  26. 72
  27. Yes
  28. No
  29. 59
  30. 45
  31. Yes
  32. 23
  33. 93
  34. 40
  35. 38
  36. 67
  37. 53
  38. 71
  39. 49
  40. 74

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