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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 793 · 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 26°. What is each of the other two angles (in degrees)?
  2. 2.In triangle ABC, angle A = 83° and angle B = 43°. What is angle C (in degrees)?
  3. 3.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  5. 5.An exterior angle of a triangle is 65°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 17 cm, 8 cm and 7 cm? (a) No (b) Yes
  9. 9.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  10. 10.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)?
  11. 11.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  12. 12.Can a triangle have sides of 10 cm, 3 cm and 18 cm? (a) Yes (b) No
  13. 13.Can a triangle have sides of 6 cm, 17 cm and 6 cm? (a) Yes (b) No
  14. 14.Can a triangle have sides of 21 cm, 9 cm and 10 cm? (a) Yes (b) No
  15. 15.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 30° and 46°. What is the exterior angle (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 50° and 24°. What is the exterior angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  22. 22.In triangle ABC, angle A = 47° and angle B = 29°. What is angle C (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  24. 24.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  26. 26.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 30° and 55°. What is the exterior angle (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  29. 29.Can a triangle have sides of 6 cm, 7 cm and 13 cm? (a) Yes (b) No
  30. 30.In triangle ABC, angle A = 79° and angle B = 62°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 82° and angle B = 22°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 36° and angle B = 91°. What is angle C (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?
  34. 34.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)?
  35. 35.The two interior opposite angles of a triangle are 79° and 21°. What is the exterior angle (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.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  38. 38.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 65° and 21°. What is the exterior angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?

Answer key

  1. 77
  2. 54
  3. 48
  4. 26
  5. 36
  6. 36
  7. 22
  8. No
  9. 26
  10. 15
  11. 10
  12. No
  13. No
  14. No
  15. 25
  16. 79
  17. 21
  18. 76
  19. 44
  20. 74
  21. 54
  22. 104
  23. 49
  24. 40
  25. 73
  26. 20
  27. 85
  28. 26
  29. No
  30. 39
  31. 76
  32. 53
  33. 38
  34. 15
  35. 100
  36. 75
  37. 90
  38. 56
  39. 86
  40. 37

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