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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 480 · 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 a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 79° and 77°. What is the exterior angle (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  4. 4.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  5. 5.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 27° and 23°. What is the exterior angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 27° and angle B = 87°. What is angle C (in degrees)?
  9. 9.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 55° and 43°. What is the exterior angle (in degrees)?
  11. 11.Can a triangle have sides of 11 cm, 3 cm and 10 cm? (a) No (b) Yes
  12. 12.Can a triangle have sides of 17 cm, 5 cm and 8 cm? (a) No (b) Yes
  13. 13.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  16. 16.In triangle ABC, angle A = 86° and angle B = 27°. What is angle C (in degrees)?
  17. 17.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)?
  18. 18.The two interior opposite angles of a triangle are 34° and 32°. What is the exterior angle (in degrees)?
  19. 19.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)?
  20. 20.In triangle ABC, angle A = 37° and angle B = 53°. What is angle C (in degrees)?
  21. 21.Can a triangle have sides of 9 cm, 9 cm and 5 cm? (a) Yes (b) No
  22. 22.In triangle ABC, angle A = 49° and angle B = 56°. What is angle C (in degrees)?
  23. 23.Can a triangle have sides of 7 cm, 16 cm and 6 cm? (a) No (b) Yes
  24. 24.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  25. 25.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  26. 26.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  27. 27.The two interior opposite angles of a triangle are 45° and 39°. What is the exterior angle (in degrees)?
  28. 28.In triangle ABC, angle A = 71° and angle B = 46°. What is angle C (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  31. 31.In triangle ABC, angle A = 62° and angle B = 72°. What is angle C (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 78° and angle B = 25°. What is angle C (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  38. 38.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)?
  39. 39.The two interior opposite angles of a triangle are 36° and 29°. What is the exterior angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?

Answer key

  1. 41
  2. 156
  3. 15
  4. 26
  5. 14
  6. 50
  7. 57
  8. 66
  9. 36
  10. 98
  11. Yes
  12. No
  13. 68
  14. 136
  15. 63
  16. 67
  17. 7
  18. 66
  19. 15
  20. 90
  21. Yes
  22. 75
  23. No
  24. 13
  25. 53
  26. 3
  27. 84
  28. 63
  29. 55
  30. 30
  31. 46
  32. 76
  33. 10
  34. 77
  35. 40
  36. 46
  37. 134
  38. 20
  39. 65
  40. 79

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