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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 137 · 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 a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  4. 4.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  6. 6.In triangle ABC, angle A = 81° and angle B = 70°. What is angle C (in degrees)?
  7. 7.Can a triangle have sides of 8 cm, 6 cm and 8 cm? (a) Yes (b) No
  8. 8.In triangle ABC, angle A = 53° and angle B = 85°. What is angle C (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  10. 10.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  11. 11.Can a triangle have sides of 15 cm, 4 cm and 12 cm? (a) Yes (b) No
  12. 12.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  13. 13.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 76° and 37°. What is the exterior angle (in degrees)?
  15. 15.In triangle ABC, angle A = 95° and angle B = 44°. What is angle C (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  17. 17.Can a triangle have sides of 7 cm, 20 cm and 9 cm? (a) Yes (b) No
  18. 18.The two interior opposite angles of a triangle are 79° and 56°. What is the exterior angle (in degrees)?
  19. 19.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  20. 20.Can a triangle have sides of 12 cm, 13 cm and 3 cm? (a) No (b) Yes
  21. 21.The two interior opposite angles of a triangle are 47° and 50°. What is the exterior angle (in degrees)?
  22. 22.Can a triangle have sides of 5 cm, 5 cm and 11 cm? (a) No (b) Yes
  23. 23.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  24. 24.In triangle ABC, angle A = 29° and angle B = 80°. What is angle C (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  26. 26.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 62° and 23°. What is the exterior angle (in degrees)?
  28. 28.Can a triangle have sides of 5 cm, 2 cm and 9 cm? (a) No (b) Yes
  29. 29.Can a triangle have sides of 10 cm, 21 cm and 9 cm? (a) Yes (b) No
  30. 30.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 45° and 64°. What is the exterior angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  33. 33.Can a triangle have sides of 3 cm, 2 cm and 4 cm? (a) No (b) Yes
  34. 34.Can a triangle have sides of 2 cm, 4 cm and 7 cm? (a) Yes (b) No
  35. 35.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  37. 37.In triangle ABC, angle A = 49° and angle B = 78°. What is angle C (in degrees)?
  38. 38.In triangle ABC, angle A = 42° and angle B = 104°. What is angle C (in degrees)?
  39. 39.In triangle ABC, angle A = 41° and angle B = 23°. What is angle C (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?

Answer key

  1. 63
  2. 25
  3. 51
  4. 50
  5. 18
  6. 29
  7. Yes
  8. 42
  9. 17
  10. 40
  11. Yes
  12. 22
  13. 21
  14. 113
  15. 41
  16. 36
  17. No
  18. 135
  19. 71
  20. Yes
  21. 97
  22. No
  23. 40
  24. 71
  25. 25
  26. 84
  27. 85
  28. No
  29. No
  30. 36
  31. 109
  32. 72
  33. Yes
  34. No
  35. 57
  36. 19
  37. 53
  38. 34
  39. 116
  40. 50

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