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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 702 · 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 121°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 63° and angle B = 80°. What is angle C (in degrees)?
  4. 4.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  5. 5.Can a triangle have sides of 4 cm, 14 cm and 10 cm? (a) Yes (b) No
  6. 6.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  7. 7.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  10. 10.An exterior angle of a triangle is 129°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  11. 11.Can a triangle have sides of 4 cm, 4 cm and 5 cm? (a) No (b) Yes
  12. 12.Can a triangle have sides of 8 cm, 23 cm and 10 cm? (a) Yes (b) No
  13. 13.In triangle ABC, angle A = 66° and angle B = 64°. What is angle C (in degrees)?
  14. 14.In triangle ABC, angle A = 85° and angle B = 67°. What is angle C (in degrees)?
  15. 15.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  17. 17.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  18. 18.Can a triangle have sides of 3 cm, 4 cm and 6 cm? (a) No (b) Yes
  19. 19.Can a triangle have sides of 21 cm, 9 cm and 11 cm? (a) No (b) Yes
  20. 20.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  21. 21.Can a triangle have sides of 10 cm, 11 cm and 11 cm? (a) Yes (b) No
  22. 22.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 72° and 25°. What is the exterior angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?
  25. 25.In triangle ABC, angle A = 78° and angle B = 42°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 65° and angle B = 86°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 11 cm, 10 cm and 3 cm? (a) No (b) Yes
  29. 29.In triangle ABC, angle A = 79° and angle B = 52°. What is angle C (in degrees)?
  30. 30.Can a triangle have sides of 7 cm, 12 cm and 22 cm? (a) Yes (b) No
  31. 31.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  34. 34.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  35. 35.An exterior angle of a triangle is 143°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  36. 36.In triangle ABC, angle A = 75° and angle B = 58°. What is angle C (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  38. 38.Can a triangle have sides of 10 cm, 10 cm and 3 cm? (a) No (b) Yes
  39. 39.The two interior opposite angles of a triangle are 25° and 69°. What is the exterior angle (in degrees)?
  40. 40.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?

Answer key

  1. 58
  2. 45
  3. 37
  4. 39
  5. No
  6. 17
  7. 30
  8. 37
  9. 17
  10. 62
  11. Yes
  12. No
  13. 50
  14. 28
  15. 31
  16. 10
  17. 72
  18. Yes
  19. No
  20. 51
  21. Yes
  22. 25
  23. 97
  24. 38
  25. 60
  26. 26
  27. 29
  28. Yes
  29. 49
  30. No
  31. 53
  32. 10
  33. 15
  34. 130
  35. 64
  36. 47
  37. 13
  38. Yes
  39. 94
  40. 58

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