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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 791 · 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.

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  1. 1.In an isosceles triangle, the angle between the two equal sides is 110°. What is each of the other two angles (in degrees)?
  2. 2.Can a triangle have sides of 8 cm, 9 cm and 3 cm? (a) No (b) Yes
  3. 3.The two interior opposite angles of a triangle are 79° and 75°. What is the exterior angle (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  5. 5.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)?
  6. 6.The two interior opposite angles of a triangle are 56° and 60°. What is the exterior angle (in degrees)?
  7. 7.Can a triangle have sides of 9 cm, 15 cm and 12 cm? (a) Yes (b) No
  8. 8.The two interior opposite angles of a triangle are 54° and 39°. What is the exterior angle (in degrees)?
  9. 9.In triangle ABC, angle A = 23° and angle B = 94°. What is angle C (in degrees)?
  10. 10.Can a triangle have sides of 8 cm, 6 cm and 14 cm? (a) Yes (b) No
  11. 11.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 26° and 59°. What is the exterior angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 51° and 64°. What is the exterior angle (in degrees)?
  15. 15.In triangle ABC, angle A = 87° and angle B = 27°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 73° and angle B = 76°. What is angle C (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  18. 18.In triangle ABC, angle A = 58° and angle B = 94°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 25° and angle B = 119°. What is angle C (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  21. 21.In triangle ABC, angle A = 39° and angle B = 84°. What is angle C (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 59° and 57°. What is the exterior angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 29° and angle B = 120°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 21° and angle B = 35°. What is angle C (in degrees)?
  28. 28.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  31. 31.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  32. 32.In triangle ABC, angle A = 69° and angle B = 44°. What is angle C (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 58° and 35°. What is the exterior angle (in degrees)?
  35. 35.In triangle ABC, angle A = 61° and angle B = 79°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 25° and angle B = 76°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 33° and 34°. What is the exterior angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 21° and 38°. What is the exterior angle (in degrees)?
  40. 40.In triangle ABC, angle A = 77° and angle B = 29°. What is angle C (in degrees)?

Answer key

  1. 35
  2. Yes
  3. 154
  4. 17
  5. 24
  6. 116
  7. Yes
  8. 93
  9. 63
  10. No
  11. 72
  12. 85
  13. 72
  14. 115
  15. 66
  16. 31
  17. 30
  18. 28
  19. 36
  20. 25
  21. 57
  22. 74
  23. 116
  24. 66
  25. 13
  26. 31
  27. 124
  28. 36
  29. 69
  30. 80
  31. 15
  32. 67
  33. 34
  34. 93
  35. 40
  36. 79
  37. 94
  38. 67
  39. 59
  40. 74

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