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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 808 · 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 : 2 : 5. What is the smallest angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  3. 3.In triangle ABC, angle A = 64° and angle B = 59°. What is angle C (in degrees)?
  4. 4.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)?
  5. 5.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 56° each. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 34° and angle B = 49°. What is angle C (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  9. 9.An exterior angle of a triangle is 149°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  11. 11.In triangle ABC, angle A = 90° and angle B = 57°. What is angle C (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 68°. 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.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  18. 18.Can a triangle have sides of 5 cm, 12 cm and 14 cm? (a) Yes (b) No
  19. 19.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)?
  20. 20.In triangle ABC, angle A = 86° and angle B = 66°. What is angle C (in degrees)?
  21. 21.Can a triangle have sides of 8 cm, 4 cm and 4 cm? (a) No (b) Yes
  22. 22.Can a triangle have sides of 11 cm, 6 cm and 15 cm? (a) Yes (b) No
  23. 23.In triangle ABC, angle A = 76° and angle B = 80°. What is angle C (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 76° and angle B = 27°. What is angle C (in degrees)?
  26. 26.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)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  28. 28.In triangle ABC, angle A = 67° and angle B = 29°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 25° and angle B = 96°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 41° and angle B = 23°. What is angle C (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  32. 32.Can a triangle have sides of 11 cm, 14 cm and 7 cm? (a) Yes (b) No
  33. 33.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  34. 34.The two interior opposite angles of a triangle are 30° and 80°. What is the exterior angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  36. 36.Can a triangle have sides of 16 cm, 9 cm and 7 cm? (a) Yes (b) No
  37. 37.The two interior opposite angles of a triangle are 77° and 56°. What is the exterior angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 40° and 65°. What is the exterior angle (in degrees)?
  39. 39.In triangle ABC, angle A = 97° and angle B = 48°. What is angle C (in degrees)?
  40. 40.An exterior angle of a triangle is 140°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?

Answer key

  1. 40
  2. 30
  3. 57
  4. 24
  5. 44
  6. 68
  7. 97
  8. 118
  9. 72
  10. 25
  11. 33
  12. 14
  13. 22
  14. 90
  15. 80
  16. 78
  17. 67
  18. Yes
  19. 15
  20. 28
  21. No
  22. Yes
  23. 24
  24. 58
  25. 77
  26. 7
  27. 41
  28. 84
  29. 59
  30. 116
  31. 36
  32. Yes
  33. 17
  34. 110
  35. 39
  36. No
  37. 133
  38. 105
  39. 35
  40. 62

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