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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 245 · 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 triangle ABC, angle A = 91° and angle B = 58°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  5. 5.In triangle ABC, angle A = 62° and angle B = 91°. What is angle C (in degrees)?
  6. 6.In triangle ABC, angle A = 45° and angle B = 35°. What is angle C (in degrees)?
  7. 7.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  8. 8.In triangle ABC, angle A = 29° and angle B = 59°. What is angle C (in degrees)?
  9. 9.In triangle ABC, angle A = 43° and angle B = 24°. What is angle C (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 23° and 67°. What is the exterior angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  15. 15.Can a triangle have sides of 5 cm, 10 cm and 11 cm? (a) No (b) Yes
  16. 16.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  17. 17.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  18. 18.Can a triangle have sides of 14 cm, 6 cm and 12 cm? (a) Yes (b) No
  19. 19.In triangle ABC, angle A = 34° and angle B = 55°. What is angle C (in degrees)?
  20. 20.In triangle ABC, angle A = 88° and angle B = 46°. What is angle C (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 36° and 46°. What is the exterior angle (in degrees)?
  22. 22.An exterior angle of a triangle is 135°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  23. 23.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  24. 24.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  25. 25.Can a triangle have sides of 9 cm, 3 cm and 12 cm? (a) No (b) Yes
  26. 26.The two interior opposite angles of a triangle are 66° and 26°. What is the exterior angle (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  28. 28.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  29. 29.The two interior opposite angles of a triangle are 56° and 52°. What is the exterior angle (in degrees)?
  30. 30.In triangle ABC, angle A = 42° and angle B = 84°. What is angle C (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  33. 33.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 25° and angle B = 54°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  36. 36.In triangle ABC, angle A = 45° and angle B = 50°. What is angle C (in degrees)?
  37. 37.An exterior angle of a triangle is 138°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  38. 38.Can a triangle have sides of 2 cm, 9 cm and 2 cm? (a) Yes (b) No
  39. 39.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?

Answer key

  1. 31
  2. 70
  3. 120
  4. 5
  5. 27
  6. 100
  7. 20
  8. 92
  9. 113
  10. 90
  11. 100
  12. 34
  13. 65
  14. 90
  15. Yes
  16. 49
  17. 3
  18. Yes
  19. 91
  20. 46
  21. 82
  22. 63
  23. 71
  24. 40
  25. No
  26. 92
  27. 17
  28. 30
  29. 108
  30. 54
  31. 18
  32. 20
  33. 138
  34. 101
  35. 72
  36. 85
  37. 62
  38. No
  39. 60
  40. 45

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