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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 597 · 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 angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  2. 2.In triangle ABC, angle A = 32° and angle B = 37°. What is angle C (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  4. 4.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  6. 6.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 47° and 36°. What is the exterior angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 52° and angle B = 81°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 75° and angle B = 42°. What is angle C (in degrees)?
  12. 12.Can a triangle have sides of 10 cm, 26 cm and 11 cm? (a) Yes (b) No
  13. 13.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  14. 14.Can a triangle have sides of 12 cm, 19 cm and 8 cm? (a) Yes (b) No
  15. 15.In triangle ABC, angle A = 34° and angle B = 60°. What is angle C (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  17. 17.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)?
  18. 18.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  19. 19.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  20. 20.Can a triangle have sides of 21 cm, 7 cm and 12 cm? (a) No (b) Yes
  21. 21.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  22. 22.In triangle ABC, angle A = 79° and angle B = 58°. What is angle C (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  24. 24.In triangle ABC, angle A = 32° and angle B = 76°. What is angle C (in degrees)?
  25. 25.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  26. 26.An exterior angle of a triangle is 49°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 61° and 74°. What is the exterior angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 63° each. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 50° and angle B = 27°. What is angle C (in degrees)?
  35. 35.An exterior angle of a triangle is 136°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  36. 36.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  37. 37.In triangle ABC, angle A = 89° and angle B = 55°. What is angle C (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  39. 39.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?

Answer key

  1. 20
  2. 111
  3. 50
  4. 22
  5. 54
  6. 61
  7. 83
  8. 23
  9. 59
  10. 47
  11. 63
  12. No
  13. 36
  14. Yes
  15. 86
  16. 78
  17. 24
  18. 30
  19. 6
  20. No
  21. 90
  22. 43
  23. 72
  24. 72
  25. 12
  26. 23
  27. 40
  28. 49
  29. 40
  30. 135
  31. 43
  32. 58
  33. 54
  34. 103
  35. 64
  36. 24
  37. 36
  38. 36
  39. 37
  40. 30

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