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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 209 · 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 : 4. What is the biggest angle (in degrees)?
  2. 2.Can a triangle have sides of 10 cm, 9 cm and 2 cm? (a) No (b) Yes
  3. 3.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  5. 5.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)?
  6. 6.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 11 cm, 9 cm and 9 cm? (a) Yes (b) No
  11. 11.In triangle ABC, angle A = 44° and angle B = 68°. What is angle C (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 82° and angle B = 76°. What is angle C (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 25° and 67°. What is the exterior angle (in degrees)?
  15. 15.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  16. 16.In triangle ABC, angle A = 34° and angle B = 36°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  19. 19.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  20. 20.In triangle ABC, angle A = 88° and angle B = 62°. What is angle C (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 27° and 30°. What is the exterior angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 69° and angle B = 65°. What is angle C (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 30° and 29°. What is the exterior angle (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 46° and angle B = 32°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 33° and angle B = 78°. What is angle C (in degrees)?
  28. 28.An exterior angle of a triangle is 138°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  29. 29.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)?
  30. 30.Can a triangle have sides of 7 cm, 4 cm and 13 cm? (a) No (b) Yes
  31. 31.In triangle ABC, angle A = 37° and angle B = 86°. What is angle C (in degrees)?
  32. 32.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  34. 34.An exterior angle of a triangle is 123°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  35. 35.Can a triangle have sides of 12 cm, 6 cm and 13 cm? (a) No (b) Yes
  36. 36.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  37. 37.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)?
  38. 38.In triangle ABC, angle A = 99° and angle B = 57°. What is angle C (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 11 cm, 22 cm and 8 cm? (a) Yes (b) No

Answer key

  1. 80
  2. Yes
  3. 90
  4. 54
  5. 12
  6. 73
  7. 34
  8. 33
  9. 24
  10. Yes
  11. 68
  12. 55
  13. 22
  14. 92
  15. 34
  16. 110
  17. 56
  18. 25
  19. 23
  20. 30
  21. 57
  22. 48
  23. 46
  24. 59
  25. 10
  26. 102
  27. 69
  28. 61
  29. 24
  30. No
  31. 57
  32. 45
  33. 90
  34. 54
  35. Yes
  36. 20
  37. 24
  38. 24
  39. 69
  40. No

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