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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 922 · 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 interior opposite angles of a triangle are 22° and 70°. What is the exterior angle (in degrees)?
  2. 2.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 124°. What is each of the other two angles (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 48° and 29°. What is the exterior angle (in degrees)?
  6. 6.Can a triangle have sides of 7 cm, 6 cm and 14 cm? (a) Yes (b) No
  7. 7.The two interior opposite angles of a triangle are 35° and 62°. What is the exterior angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 69° and 37°. What is the exterior angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  12. 12.Can a triangle have sides of 21 cm, 11 cm and 9 cm? (a) Yes (b) No
  13. 13.In triangle ABC, angle A = 24° and angle B = 54°. What is angle C (in degrees)?
  14. 14.In triangle ABC, angle A = 83° and angle B = 55°. What is angle C (in degrees)?
  15. 15.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  16. 16.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)?
  17. 17.In triangle ABC, angle A = 80° and angle B = 35°. What is angle C (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 72° and 54°. What is the exterior angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  22. 22.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  24. 24.An exterior angle of a triangle is 125°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  28. 28.The two interior opposite angles of a triangle are 39° and 24°. What is the exterior angle (in degrees)?
  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.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)?
  31. 31.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  32. 32.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  34. 34.In triangle ABC, angle A = 35° and angle B = 20°. What is angle C (in degrees)?
  35. 35.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)?
  36. 36.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  37. 37.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  38. 38.In triangle ABC, angle A = 73° and angle B = 59°. What is angle C (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 9 cm, 3 cm and 12 cm? (a) Yes (b) No

Answer key

  1. 92
  2. 69
  3. 20
  4. 28
  5. 77
  6. No
  7. 97
  8. 106
  9. 54
  10. 20
  11. 120
  12. No
  13. 102
  14. 42
  15. 20
  16. 8
  17. 65
  18. 126
  19. 39
  20. 18
  21. 72
  22. 45
  23. 48
  24. 76
  25. 90
  26. 90
  27. 25
  28. 63
  29. 4
  30. 9
  31. 21
  32. 45
  33. 60
  34. 125
  35. 15
  36. 25
  37. 20
  38. 48
  39. 76
  40. No

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