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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 466 · 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.

NameDateTime takenScore ___ / 40
  1. 1.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  3. 3.The two interior opposite angles of a triangle are 35° and 33°. What is the exterior angle (in degrees)?
  4. 4.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  5. 5.Can a triangle have sides of 7 cm, 2 cm and 13 cm? (a) Yes (b) No
  6. 6.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  7. 7.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 32° and 61°. What is the exterior angle (in degrees)?
  13. 13.Can a triangle have sides of 12 cm, 8 cm and 22 cm? (a) Yes (b) No
  14. 14.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  15. 15.The two interior opposite angles of a triangle are 29° and 31°. What is the exterior angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?
  22. 22.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  25. 25.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)?
  26. 26.In triangle ABC, angle A = 68° and angle B = 39°. What is angle C (in degrees)?
  27. 27.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 69° and angle B = 42°. What is angle C (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  32. 32.In triangle ABC, angle A = 67° and angle B = 60°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 98° and angle B = 32°. What is angle C (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  36. 36.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  37. 37.Can a triangle have sides of 8 cm, 7 cm and 2 cm? (a) No (b) Yes
  38. 38.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  39. 39.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?

Answer key

  1. 75
  2. 10
  3. 68
  4. 75
  5. No
  6. 17
  7. 122
  8. 46
  9. 39
  10. 20
  11. 34
  12. 93
  13. No
  14. 5
  15. 60
  16. 20
  17. 23
  18. 90
  19. 16
  20. 90
  21. 79
  22. 74
  23. 120
  24. 20
  25. 12
  26. 73
  27. 40
  28. 31
  29. 72
  30. 69
  31. 36
  32. 53
  33. 50
  34. 14
  35. 19
  36. 21
  37. Yes
  38. 39
  39. 40
  40. 86

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