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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 186 · 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 angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  2. 2.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  3. 3.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)?
  4. 4.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  6. 6.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  7. 7.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  8. 8.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)?
  9. 9.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  10. 10.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 44° and 76°. What is the exterior angle (in degrees)?
  13. 13.In triangle ABC, angle A = 98° and angle B = 54°. What is angle C (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  15. 15.In triangle ABC, angle A = 38° and angle B = 39°. What is angle C (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  18. 18.In triangle ABC, angle A = 51° and angle B = 62°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 38° and angle B = 51°. What is angle C (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  21. 21.The two interior opposite angles of a triangle are 46° and 42°. What is the exterior angle (in degrees)?
  22. 22.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)?
  23. 23.An exterior angle of a triangle is 51°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  24. 24.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 91° and angle B = 68°. What is angle C (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 44° and 70°. What is the exterior angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 47° and 48°. What is the exterior angle (in degrees)?
  32. 32.In triangle ABC, angle A = 98° and angle B = 32°. What is angle C (in degrees)?
  33. 33.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  34. 34.Can a triangle have sides of 5 cm, 12 cm and 14 cm? (a) No (b) Yes
  35. 35.Can a triangle have sides of 2 cm, 12 cm and 6 cm? (a) Yes (b) No
  36. 36.An exterior angle of a triangle is 59°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  37. 37.Can a triangle have sides of 4 cm, 11 cm and 3 cm? (a) No (b) Yes
  38. 38.Can a triangle have sides of 9 cm, 7 cm and 7 cm? (a) No (b) Yes
  39. 39.Can a triangle have sides of 3 cm, 7 cm and 7 cm? (a) No (b) Yes
  40. 40.In triangle ABC, angle A = 26° and angle B = 124°. What is angle C (in degrees)?

Answer key

  1. 90
  2. 44
  3. 7
  4. 36
  5. 72
  6. 79
  7. 47
  8. 24
  9. 12
  10. 66
  11. 59
  12. 120
  13. 28
  14. 20
  15. 103
  16. 35
  17. 25
  18. 67
  19. 91
  20. 17
  21. 88
  22. 8
  23. 22
  24. 75
  25. 69
  26. 21
  27. 72
  28. 102
  29. 114
  30. 100
  31. 95
  32. 50
  33. 24
  34. Yes
  35. No
  36. 33
  37. No
  38. Yes
  39. Yes
  40. 30

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