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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 158 · 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 8 cm and 6 cm. How long is the longest side (in cm)?
  2. 2.In triangle ABC, angle A = 90° and angle B = 54°. What is angle C (in degrees)?
  3. 3.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)?
  4. 4.The two interior opposite angles of a triangle are 41° and 77°. What is the exterior angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 37° and angle B = 58°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  10. 10.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  11. 11.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  12. 12.In triangle ABC, angle A = 75° and angle B = 61°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  14. 14.Can a triangle have sides of 22 cm, 12 cm and 9 cm? (a) No (b) Yes
  15. 15.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  16. 16.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  18. 18.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)?
  19. 19.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 88° and angle B = 50°. What is angle C (in degrees)?
  24. 24.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 78° and 25°. What is the exterior angle (in degrees)?
  27. 27.In triangle ABC, angle A = 99° and angle B = 58°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 6 cm, 8 cm and 3 cm? (a) No (b) Yes
  29. 29.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  30. 30.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  31. 31.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  32. 32.The two interior opposite angles of a triangle are 60° and 63°. What is the exterior angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  34. 34.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  35. 35.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  36. 36.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  37. 37.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  38. 38.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?

Answer key

  1. 10
  2. 36
  3. 15
  4. 118
  5. 40
  6. 136
  7. 85
  8. 100
  9. 65
  10. 12
  11. 44
  12. 44
  13. 124
  14. No
  15. 17
  16. 73
  17. 26
  18. 24
  19. 45
  20. 68
  21. 71
  22. 27
  23. 42
  24. 72
  25. 90
  26. 103
  27. 23
  28. Yes
  29. 4
  30. 44
  31. 20
  32. 123
  33. 17
  34. 37
  35. 28
  36. 40
  37. 64
  38. 33
  39. 112
  40. 90

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