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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 968 · 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.Can a triangle have sides of 6 cm, 3 cm and 9 cm? (a) Yes (b) No
  2. 2.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)?
  3. 3.Can a triangle have sides of 9 cm, 8 cm and 8 cm? (a) Yes (b) No
  4. 4.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  5. 5.In triangle ABC, angle A = 79° and angle B = 80°. What is angle C (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  7. 7.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  8. 8.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  9. 9.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  10. 10.In triangle ABC, angle A = 78° and angle B = 34°. What is angle C (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  12. 12.An exterior angle of a triangle is 55°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  13. 13.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  17. 17.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  18. 18.An exterior angle of a triangle is 78°. 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 71°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  20. 20.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  21. 21.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 76° and 27°. What is the exterior angle (in degrees)?
  24. 24.In triangle ABC, angle A = 62° and angle B = 53°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  26. 26.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  27. 27.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)?
  28. 28.Can a triangle have sides of 15 cm, 8 cm and 12 cm? (a) No (b) Yes
  29. 29.In triangle ABC, angle A = 90° and angle B = 64°. What is angle C (in degrees)?
  30. 30.Can a triangle have sides of 13 cm, 9 cm and 9 cm? (a) Yes (b) No
  31. 31.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 36° and angle B = 47°. What is angle C (in degrees)?
  39. 39.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  40. 40.Can a triangle have sides of 3 cm, 2 cm and 4 cm? (a) Yes (b) No

Answer key

  1. No
  2. 15
  3. Yes
  4. 61
  5. 21
  6. 35
  7. 36
  8. 13
  9. 36
  10. 68
  11. 79
  12. 21
  13. 24
  14. 15
  15. 56
  16. 108
  17. 15
  18. 50
  19. 43
  20. 58
  21. 20
  22. 120
  23. 103
  24. 65
  25. 77
  26. 20
  27. 6
  28. Yes
  29. 26
  30. Yes
  31. 49
  32. 23
  33. 71
  34. 64
  35. 80
  36. 50
  37. 90
  38. 97
  39. 75
  40. Yes

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