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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 673 · 40 sums
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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.

NameDateTime takenScore ___ / 40
  1. 1.Can a triangle have sides of 10 cm, 20 cm and 6 cm? (a) Yes (b) No
  2. 2.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 40° and 66°. What is the exterior angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  5. 5.In triangle ABC, angle A = 20° and angle B = 79°. What is angle C (in degrees)?
  6. 6.In triangle ABC, angle A = 55° and angle B = 25°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  9. 9.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  10. 10.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  12. 12.In triangle ABC, angle A = 37° and angle B = 101°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  14. 14.Can a triangle have sides of 5 cm, 8 cm and 10 cm? (a) No (b) Yes
  15. 15.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  16. 16.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  18. 18.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  19. 19.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  20. 20.In triangle ABC, angle A = 58° and angle B = 79°. What is angle C (in degrees)?
  21. 21.Can a triangle have sides of 4 cm, 10 cm and 18 cm? (a) Yes (b) No
  22. 22.In triangle ABC, angle A = 98° and angle B = 37°. What is angle C (in degrees)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 28° and angle B = 32°. What is angle C (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  28. 28.Can a triangle have sides of 9 cm, 10 cm and 10 cm? (a) No (b) Yes
  29. 29.In triangle ABC, angle A = 82° and angle B = 63°. What is angle C (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 68° and 29°. What is the exterior angle (in degrees)?
  31. 31.An exterior angle of a triangle is 129°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  34. 34.In triangle ABC, angle A = 90° and angle B = 56°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  36. 36.In triangle ABC, angle A = 24° and angle B = 51°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  39. 39.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  40. 40.In triangle ABC, angle A = 31° and angle B = 66°. What is angle C (in degrees)?

Answer key

  1. No
  2. 12
  3. 106
  4. 90
  5. 81
  6. 100
  7. 63
  8. 58
  9. 67
  10. 45
  11. 80
  12. 42
  13. 23
  14. Yes
  15. 44
  16. 50
  17. 13
  18. 22
  19. 70
  20. 43
  21. No
  22. 45
  23. 38
  24. 78
  25. 120
  26. 64
  27. 24
  28. Yes
  29. 35
  30. 97
  31. 67
  32. 15
  33. 15
  34. 34
  35. 75
  36. 105
  37. 62
  38. 14
  39. 20
  40. 83

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