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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 672 · 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 129°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  3. 3.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 89° and angle B = 63°. What is angle C (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 61° each. What is the third angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 69° and 70°. What is the exterior angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  8. 8.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  9. 9.Can a triangle have sides of 10 cm, 12 cm and 10 cm? (a) Yes (b) No
  10. 10.Can a triangle have sides of 5 cm, 5 cm and 10 cm? (a) Yes (b) No
  11. 11.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 68° and 20°. What is the exterior angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles (in degrees)?
  16. 16.In triangle ABC, angle A = 47° and angle B = 78°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 64°. What is each of the other two angles (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 52° and 74°. What is the exterior angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  21. 21.Can a triangle have sides of 8 cm, 8 cm and 20 cm? (a) No (b) Yes
  22. 22.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 51° and angle B = 102°. What is angle C (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 54° each. What is the third angle (in degrees)?
  28. 28.Can a triangle have sides of 10 cm, 6 cm and 4 cm? (a) Yes (b) No
  29. 29.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 26° and 27°. What is the exterior angle (in degrees)?
  31. 31.Can a triangle have sides of 24 cm, 11 cm and 10 cm? (a) No (b) Yes
  32. 32.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  36. 36.In triangle ABC, angle A = 75° and angle B = 36°. What is angle C (in degrees)?
  37. 37.In triangle ABC, angle A = 32° and angle B = 112°. What is angle C (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 43° and 53°. What is the exterior angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  40. 40.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?

Answer key

  1. 76
  2. 15
  3. 46
  4. 28
  5. 58
  6. 139
  7. 18
  8. 27
  9. Yes
  10. No
  11. 9
  12. 61
  13. 20
  14. 88
  15. 30
  16. 55
  17. 61
  18. 58
  19. 126
  20. 10
  21. No
  22. 14
  23. 24
  24. 27
  25. 30
  26. 120
  27. 72
  28. No
  29. 79
  30. 53
  31. No
  32. 17
  33. 71
  34. 58
  35. 30
  36. 69
  37. 36
  38. 96
  39. 80
  40. 8

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