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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 625 · 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.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  4. 4.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  6. 6.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  7. 7.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 34° and angle B = 59°. What is angle C (in degrees)?
  11. 11.Can a triangle have sides of 18 cm, 9 cm and 7 cm? (a) Yes (b) No
  12. 12.In triangle ABC, angle A = 42° and angle B = 111°. What is angle C (in degrees)?
  13. 13.In triangle ABC, angle A = 37° and angle B = 44°. What is angle C (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 29° and 41°. What is the exterior angle (in degrees)?
  15. 15.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  16. 16.Can a triangle have sides of 20 cm, 8 cm and 8 cm? (a) Yes (b) No
  17. 17.The two interior opposite angles of a triangle are 64° and 55°. What is the exterior angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  20. 20.An exterior angle of a triangle is 134°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 61° and angle B = 80°. What is angle C (in degrees)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 5 cm, 9 cm and 12 cm? (a) Yes (b) No
  27. 27.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  29. 29.In triangle ABC, angle A = 27° and angle B = 50°. What is angle C (in degrees)?
  30. 30.An exterior angle of a triangle is 142°. One of its two interior opposite angles is 66°. What is the other one (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.Can a triangle have sides of 5 cm, 10 cm and 12 cm? (a) No (b) Yes
  33. 33.The two interior opposite angles of a triangle are 75° and 60°. What is the exterior angle (in degrees)?
  34. 34.In triangle ABC, angle A = 95° and angle B = 49°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  36. 36.Can a triangle have sides of 9 cm, 4 cm and 5 cm? (a) No (b) Yes
  37. 37.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 79° and 26°. What is the exterior angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?

Answer key

  1. 39
  2. 45
  3. 17
  4. 30
  5. 130
  6. 25
  7. 21
  8. 63
  9. 112
  10. 87
  11. No
  12. 27
  13. 99
  14. 70
  15. 28
  16. No
  17. 119
  18. 90
  19. 65
  20. 67
  21. 20
  22. 39
  23. 37
  24. 57
  25. 11
  26. Yes
  27. 8
  28. 66
  29. 103
  30. 76
  31. 120
  32. Yes
  33. 135
  34. 36
  35. 90
  36. No
  37. 72
  38. 105
  39. 90
  40. 73

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