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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 768 · 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 longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  2. 2.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  3. 3.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  4. 4.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (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 two interior opposite angles of a triangle are 21° and 67°. What is the exterior angle (in degrees)?
  7. 7.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  8. 8.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  9. 9.Can a triangle have sides of 10 cm, 11 cm and 23 cm? (a) Yes (b) No
  10. 10.In an isosceles triangle, the angle between the two equal sides is 158°. What is each of the other two angles (in degrees)?
  11. 11.Can a triangle have sides of 9 cm, 7 cm and 6 cm? (a) Yes (b) No
  12. 12.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  14. 14.In triangle ABC, angle A = 65° and angle B = 25°. What is angle C (in degrees)?
  15. 15.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)?
  16. 16.Can a triangle have sides of 12 cm, 13 cm and 5 cm? (a) Yes (b) No
  17. 17.In triangle ABC, angle A = 63° and angle B = 23°. What is angle C (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  19. 19.Can a triangle have sides of 12 cm, 23 cm and 6 cm? (a) Yes (b) No
  20. 20.Can a triangle have sides of 9 cm, 3 cm and 10 cm? (a) Yes (b) No
  21. 21.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  22. 22.Can a triangle have sides of 11 cm, 19 cm and 7 cm? (a) Yes (b) No
  23. 23.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  25. 25.Can a triangle have sides of 7 cm, 3 cm and 6 cm? (a) Yes (b) No
  26. 26.Can a triangle have sides of 5 cm, 21 cm and 11 cm? (a) Yes (b) No
  27. 27.The two interior opposite angles of a triangle are 80° and 80°. What is the exterior angle (in degrees)?
  28. 28.In triangle ABC, angle A = 58° and angle B = 31°. What is angle C (in degrees)?
  29. 29.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  30. 30.Can a triangle have sides of 21 cm, 12 cm and 6 cm? (a) No (b) Yes
  31. 31.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 11 cm, 8 cm and 3 cm? (a) Yes (b) No
  33. 33.In triangle ABC, angle A = 68° and angle B = 35°. What is angle C (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 87° and angle B = 68°. What is angle C (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  38. 38.An exterior angle of a triangle is 133°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 58° and 64°. What is the exterior angle (in degrees)?

Answer key

  1. 4
  2. 72
  3. 40
  4. 70
  5. 48
  6. 88
  7. 41
  8. 59
  9. No
  10. 11
  11. Yes
  12. 50
  13. 62
  14. 90
  15. 15
  16. Yes
  17. 94
  18. 90
  19. No
  20. Yes
  21. 50
  22. No
  23. 114
  24. 90
  25. Yes
  26. No
  27. 160
  28. 91
  29. 36
  30. No
  31. 41
  32. No
  33. 77
  34. 44
  35. 25
  36. 11
  37. 17
  38. 80
  39. 90
  40. 122

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