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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 900 · 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 = 31° and angle B = 80°. What is angle C (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 96°. What is each of the other two angles (in degrees)?
  3. 3.Can a triangle have sides of 13 cm, 5 cm and 9 cm? (a) Yes (b) No
  4. 4.In triangle ABC, angle A = 62° and angle B = 53°. What is angle C (in degrees)?
  5. 5.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  6. 6.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  7. 7.In triangle ABC, angle A = 46° and angle B = 73°. What is angle C (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  10. 10.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 42° and 80°. What is the exterior angle (in degrees)?
  13. 13.In triangle ABC, angle A = 53° and angle B = 74°. What is angle C (in degrees)?
  14. 14.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)?
  15. 15.Can a triangle have sides of 7 cm, 8 cm and 5 cm? (a) No (b) Yes
  16. 16.Can a triangle have sides of 9 cm, 16 cm and 8 cm? (a) Yes (b) No
  17. 17.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  18. 18.Can a triangle have sides of 7 cm, 3 cm and 11 cm? (a) Yes (b) No
  19. 19.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  22. 22.An exterior angle of a triangle is 120°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  23. 23.Can a triangle have sides of 7 cm, 11 cm and 11 cm? (a) No (b) Yes
  24. 24.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 3 cm, 11 cm and 11 cm? (a) No (b) Yes
  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.The two interior opposite angles of a triangle are 70° and 51°. What is the exterior angle (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 55° and angle B = 49°. What is angle C (in degrees)?
  31. 31.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  33. 33.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 68° and angle B = 24°. What is angle C (in degrees)?
  36. 36.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  37. 37.An exterior angle of a triangle is 121°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  38. 38.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  39. 39.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  40. 40.In triangle ABC, angle A = 40° and angle B = 28°. What is angle C (in degrees)?

Answer key

  1. 69
  2. 42
  3. Yes
  4. 65
  5. 48
  6. 6
  7. 61
  8. 112
  9. 25
  10. 63
  11. 80
  12. 122
  13. 53
  14. 3
  15. Yes
  16. Yes
  17. 13
  18. No
  19. 40
  20. 45
  21. 21
  22. 80
  23. Yes
  24. 20
  25. Yes
  26. 7
  27. 121
  28. 78
  29. 106
  30. 76
  31. 36
  32. 13
  33. 65
  34. 45
  35. 88
  36. 75
  37. 47
  38. 16
  39. 25
  40. 112

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