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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 967 · 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 a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  3. 3.In triangle ABC, angle A = 59° and angle B = 65°. What is angle C (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 37° and 52°. What is the exterior angle (in degrees)?
  5. 5.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)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  7. 7.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  8. 8.In triangle ABC, angle A = 70° and angle B = 59°. What is angle C (in degrees)?
  9. 9.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  10. 10.Can a triangle have sides of 12 cm, 14 cm and 9 cm? (a) No (b) Yes
  11. 11.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  12. 12.Can a triangle have sides of 8 cm, 6 cm and 7 cm? (a) Yes (b) No
  13. 13.In triangle ABC, angle A = 78° and angle B = 33°. What is angle C (in degrees)?
  14. 14.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 20° and 35°. What is the exterior angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  21. 21.In triangle ABC, angle A = 68° and angle B = 76°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 22° and angle B = 104°. What is angle C (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  25. 25.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 28° and 38°. What is the exterior angle (in degrees)?
  28. 28.An exterior angle of a triangle is 123°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  29. 29.An exterior angle of a triangle is 65°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 61° and 34°. What is the exterior angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  33. 33.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 53° and 80°. What is the exterior angle (in degrees)?
  37. 37.In triangle ABC, angle A = 78° and angle B = 35°. What is angle C (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?

Answer key

  1. 18
  2. 25
  3. 56
  4. 89
  5. 12
  6. 64
  7. 77
  8. 51
  9. 60
  10. Yes
  11. 41
  12. Yes
  13. 69
  14. 84
  15. 51
  16. 100
  17. 39
  18. 40
  19. 55
  20. 30
  21. 36
  22. 54
  23. 27
  24. 25
  25. 20
  26. 50
  27. 66
  28. 62
  29. 38
  30. 17
  31. 95
  32. 90
  33. 29
  34. 58
  35. 45
  36. 133
  37. 67
  38. 13
  39. 57
  40. 12

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