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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 859 · 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 two interior opposite angles of a triangle are 76° and 77°. What is the exterior angle (in degrees)?
  2. 2.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)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  4. 4.In triangle ABC, angle A = 46° and angle B = 80°. What is angle C (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 52° and 56°. What is the exterior angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 23° and 35°. What is the exterior angle (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  10. 10.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  12. 12.The two interior opposite angles of a triangle are 47° and 70°. What is the exterior angle (in degrees)?
  13. 13.Can a triangle have sides of 3 cm, 3 cm and 2 cm? (a) No (b) Yes
  14. 14.In triangle ABC, angle A = 82° and angle B = 50°. What is angle C (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 58° and 49°. What is the exterior angle (in degrees)?
  16. 16.In triangle ABC, angle A = 84° and angle B = 67°. What is angle C (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  19. 19.In triangle ABC, angle A = 81° and angle B = 22°. What is angle C (in degrees)?
  20. 20.Can a triangle have sides of 20 cm, 11 cm and 7 cm? (a) Yes (b) No
  21. 21.In triangle ABC, angle A = 24° and angle B = 61°. What is angle C (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  24. 24.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  25. 25.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  26. 26.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  27. 27.Can a triangle have sides of 21 cm, 7 cm and 11 cm? (a) No (b) Yes
  28. 28.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 7 cm, 7 cm and 3 cm? (a) Yes (b) No
  30. 30.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 42° and angle B = 109°. What is angle C (in degrees)?
  32. 32.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 76° and 37°. What is the exterior angle (in degrees)?
  35. 35.An exterior angle of a triangle is 147°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  36. 36.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 54° and 62°. What is the exterior angle (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  39. 39.The two interior opposite angles of a triangle are 47° and 44°. What is the exterior angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 40° and 25°. What is the exterior angle (in degrees)?

Answer key

  1. 153
  2. 12
  3. 29
  4. 54
  5. 108
  6. 58
  7. 100
  8. 72
  9. 50
  10. 48
  11. 17
  12. 117
  13. Yes
  14. 48
  15. 107
  16. 29
  17. 27
  18. 120
  19. 77
  20. No
  21. 95
  22. 74
  23. 23
  24. 34
  25. 8
  26. 20
  27. No
  28. 76
  29. Yes
  30. 51
  31. 29
  32. 36
  33. 36
  34. 113
  35. 78
  36. 45
  37. 116
  38. 25
  39. 91
  40. 65

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