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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 556 · 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 1 : 2 : 2. What is the smallest angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  3. 3.Can a triangle have sides of 10 cm, 12 cm and 2 cm? (a) No (b) Yes
  4. 4.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)?
  5. 5.In triangle ABC, angle A = 85° and angle B = 20°. What is angle C (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  8. 8.Can a triangle have sides of 8 cm, 9 cm and 8 cm? (a) No (b) Yes
  9. 9.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  10. 10.Can a triangle have sides of 5 cm, 4 cm and 3 cm? (a) Yes (b) No
  11. 11.The two interior opposite angles of a triangle are 41° and 28°. What is the exterior angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  13. 13.In triangle ABC, angle A = 64° and angle B = 39°. What is angle C (in degrees)?
  14. 14.In triangle ABC, angle A = 28° and angle B = 115°. What is angle C (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 110°. What is each of the other two angles (in degrees)?
  16. 16.Can a triangle have sides of 9 cm, 9 cm and 23 cm? (a) Yes (b) No
  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.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  19. 19.An exterior angle of a triangle is 58°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  20. 20.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  21. 21.Can a triangle have sides of 9 cm, 10 cm and 22 cm? (a) Yes (b) No
  22. 22.In triangle ABC, angle A = 100° and angle B = 32°. What is angle C (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 63° and 55°. What is the exterior angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  26. 26.In triangle ABC, angle A = 39° and angle B = 93°. What is angle C (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  28. 28.Can a triangle have sides of 7 cm, 2 cm and 13 cm? (a) Yes (b) No
  29. 29.In triangle ABC, angle A = 100° and angle B = 49°. What is angle C (in degrees)?
  30. 30.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  31. 31.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  32. 32.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  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 = 42° and angle B = 45°. What is angle C (in degrees)?
  35. 35.Can a triangle have sides of 2 cm, 7 cm and 6 cm? (a) Yes (b) No
  36. 36.The two interior opposite angles of a triangle are 68° and 65°. What is the exterior angle (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 2 cm, 4 cm and 4 cm? (a) Yes (b) No
  39. 39.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 74° and 59°. What is the exterior angle (in degrees)?

Answer key

  1. 36
  2. 80
  3. No
  4. 8
  5. 75
  6. 90
  7. 50
  8. Yes
  9. 72
  10. Yes
  11. 69
  12. 84
  13. 77
  14. 37
  15. 35
  16. No
  17. 3
  18. 65
  19. 26
  20. 32
  21. No
  22. 48
  23. 118
  24. 90
  25. 61
  26. 48
  27. 14
  28. No
  29. 31
  30. 90
  31. 25
  32. 52
  33. 138
  34. 93
  35. Yes
  36. 133
  37. 64
  38. Yes
  39. 39
  40. 133

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