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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 403 · 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 an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  2. 2.Can a triangle have sides of 10 cm, 8 cm and 11 cm? (a) Yes (b) No
  3. 3.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)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 60° and 64°. What is the exterior angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  7. 7.In triangle ABC, angle A = 42° and angle B = 89°. What is angle C (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  9. 9.An exterior angle of a triangle is 65°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  10. 10.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  11. 11.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  12. 12.In triangle ABC, angle A = 92° and angle B = 50°. What is angle C (in degrees)?
  13. 13.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  14. 14.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  15. 15.Can a triangle have sides of 9 cm, 23 cm and 9 cm? (a) No (b) Yes
  16. 16.The two interior opposite angles of a triangle are 22° and 22°. What is the exterior angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 7 cm, 2 cm and 2 cm? (a) No (b) Yes
  19. 19.In triangle ABC, angle A = 58° and angle B = 63°. What is angle C (in degrees)?
  20. 20.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  21. 21.In triangle ABC, angle A = 67° and angle B = 47°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 88° and angle B = 29°. What is angle C (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  25. 25.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  27. 27.Can a triangle have sides of 5 cm, 8 cm and 11 cm? (a) No (b) Yes
  28. 28.Can a triangle have sides of 13 cm, 2 cm and 10 cm? (a) Yes (b) No
  29. 29.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  32. 32.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  33. 33.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  34. 34.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  35. 35.In triangle ABC, angle A = 74° and angle B = 44°. What is angle C (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  37. 37.In triangle ABC, angle A = 41° and angle B = 43°. What is angle C (in degrees)?
  38. 38.In triangle ABC, angle A = 22° and angle B = 99°. What is angle C (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 42° and 46°. What is the exterior angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?

Answer key

  1. 48
  2. Yes
  3. 15
  4. 38
  5. 124
  6. 90
  7. 49
  8. 15
  9. 21
  10. 24
  11. 36
  12. 38
  13. 52
  14. 8
  15. No
  16. 44
  17. 61
  18. No
  19. 59
  20. 42
  21. 66
  22. 63
  23. 72
  24. 26
  25. 36
  26. 17
  27. Yes
  28. No
  29. 41
  30. 90
  31. 72
  32. 12
  33. 77
  34. 34
  35. 62
  36. 51
  37. 96
  38. 59
  39. 88
  40. 12

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