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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 57 · 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 116°. What is each of the other two angles (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  5. 5.In triangle ABC, angle A = 45° and angle B = 30°. What is angle C (in degrees)?
  6. 6.In triangle ABC, angle A = 67° and angle B = 43°. What is angle C (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 23 cm, 12 cm and 8 cm? (a) Yes (b) No
  11. 11.In triangle ABC, angle A = 94° and angle B = 37°. What is angle C (in degrees)?
  12. 12.In triangle ABC, angle A = 35° and angle B = 27°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  14. 14.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  15. 15.Can a triangle have sides of 6 cm, 3 cm and 7 cm? (a) No (b) Yes
  16. 16.In triangle ABC, angle A = 40° and angle B = 104°. What is angle C (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 64° and 52°. What is the exterior angle (in degrees)?
  19. 19.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)?
  20. 20.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  21. 21.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  22. 22.The two interior opposite angles of a triangle are 43° and 74°. What is the exterior angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  25. 25.An exterior angle of a triangle is 51°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 48° and 29°. What is the exterior angle (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  30. 30.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?
  32. 32.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 57° and 23°. What is the exterior angle (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  36. 36.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest 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. 32
  2. 18
  3. 49
  4. 112
  5. 105
  6. 70
  7. 63
  8. 55
  9. 13
  10. No
  11. 49
  12. 118
  13. 34
  14. 56
  15. Yes
  16. 36
  17. 69
  18. 116
  19. 16
  20. 40
  21. 12
  22. 117
  23. 75
  24. 30
  25. 22
  26. 52
  27. 64
  28. 77
  29. 30
  30. 75
  31. 96
  32. 56
  33. 37
  34. 80
  35. 106
  36. 66
  37. 77
  38. 68
  39. 36
  40. 12

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