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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 240 · 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 triangle ABC, angle A = 75° and angle B = 48°. What is angle C (in degrees)?
  2. 2.In triangle ABC, angle A = 46° and angle B = 23°. What is angle C (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 35° and 53°. What is the exterior angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 85° and angle B = 72°. What is angle C (in degrees)?
  7. 7.Can a triangle have sides of 12 cm, 21 cm and 6 cm? (a) Yes (b) No
  8. 8.In triangle ABC, angle A = 66° and angle B = 27°. What is angle C (in degrees)?
  9. 9.In triangle ABC, angle A = 96° and angle B = 30°. What is angle C (in degrees)?
  10. 10.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  11. 11.Can a triangle have sides of 6 cm, 12 cm and 9 cm? (a) No (b) Yes
  12. 12.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 34° and 34°. What is the exterior angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  17. 17.Can a triangle have sides of 2 cm, 3 cm and 3 cm? (a) Yes (b) No
  18. 18.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  19. 19.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  20. 20.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  23. 23.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)?
  24. 24.In triangle ABC, angle A = 86° and angle B = 29°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 78° and angle B = 32°. What is angle C (in degrees)?
  26. 26.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  27. 27.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  30. 30.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  31. 31.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 56° and 43°. What is the exterior angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  34. 34.In triangle ABC, angle A = 49° and angle B = 83°. What is angle C (in degrees)?
  35. 35.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 62° and 70°. What is the exterior angle (in degrees)?
  37. 37.In triangle ABC, angle A = 42° and angle B = 21°. What is angle C (in degrees)?
  38. 38.Can a triangle have sides of 6 cm, 1 cm and 6 cm? (a) Yes (b) No
  39. 39.Can a triangle have sides of 7 cm, 8 cm and 8 cm? (a) Yes (b) No
  40. 40.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?

Answer key

  1. 57
  2. 111
  3. 88
  4. 70
  5. 120
  6. 23
  7. No
  8. 87
  9. 54
  10. 24
  11. Yes
  12. 33
  13. 68
  14. 73
  15. 90
  16. 72
  17. Yes
  18. 77
  19. 39
  20. 84
  21. 128
  22. 84
  23. 8
  24. 65
  25. 70
  26. 7
  27. 50
  28. 74
  29. 43
  30. 50
  31. 50
  32. 99
  33. 36
  34. 48
  35. 51
  36. 132
  37. 117
  38. Yes
  39. Yes
  40. 20

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