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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 199 · 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.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (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.Can a triangle have sides of 12 cm, 20 cm and 7 cm? (a) No (b) Yes
  4. 4.In triangle ABC, angle A = 21° and angle B = 61°. What is angle C (in degrees)?
  5. 5.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  6. 6.Can a triangle have sides of 11 cm, 6 cm and 21 cm? (a) No (b) Yes
  7. 7.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  8. 8.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  9. 9.An exterior angle of a triangle is 139°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  10. 10.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (in degrees)?
  13. 13.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  17. 17.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 6 cm, 8 cm and 17 cm? (a) No (b) Yes
  19. 19.In triangle ABC, angle A = 29° and angle B = 53°. What is angle C (in degrees)?
  20. 20.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  22. 22.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)?
  23. 23.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  24. 24.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  25. 25.Can a triangle have sides of 4 cm, 11 cm and 10 cm? (a) No (b) Yes
  26. 26.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 66° and 27°. What is the exterior angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  29. 29.In triangle ABC, angle A = 97° and angle B = 26°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 49° and angle B = 24°. What is angle C (in degrees)?
  31. 31.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  32. 32.Can a triangle have sides of 5 cm, 12 cm and 11 cm? (a) Yes (b) No
  33. 33.In triangle ABC, angle A = 24° and angle B = 100°. What is angle C (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 36° and 33°. What is the exterior angle (in degrees)?
  35. 35.In triangle ABC, angle A = 33° and angle B = 64°. What is angle C (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 154°. What is each of the other two angles (in degrees)?
  38. 38.Can a triangle have sides of 12 cm, 17 cm and 4 cm? (a) No (b) Yes
  39. 39.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?

Answer key

  1. 36
  2. 17
  3. No
  4. 98
  5. 38
  6. No
  7. 50
  8. 7
  9. 63
  10. 18
  11. 90
  12. 68
  13. 64
  14. 17
  15. 40
  16. 25
  17. 13
  18. No
  19. 98
  20. 75
  21. 72
  22. 15
  23. 66
  24. 15
  25. Yes
  26. 73
  27. 93
  28. 100
  29. 57
  30. 107
  31. 57
  32. Yes
  33. 56
  34. 69
  35. 83
  36. 25
  37. 13
  38. No
  39. 71
  40. 32

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