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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 538 · 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 5 : 6 : 7. What is the smallest angle (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  3. 3.In triangle ABC, angle A = 57° and angle B = 71°. What is angle C (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  6. 6.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  8. 8.Can a triangle have sides of 10 cm, 6 cm and 6 cm? (a) No (b) Yes
  9. 9.The two interior opposite angles of a triangle are 21° and 21°. What is the exterior angle (in degrees)?
  10. 10.In triangle ABC, angle A = 36° and angle B = 32°. What is angle C (in degrees)?
  11. 11.Can a triangle have sides of 10 cm, 6 cm and 16 cm? (a) Yes (b) No
  12. 12.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  14. 14.Can a triangle have sides of 12 cm, 22 cm and 10 cm? (a) Yes (b) No
  15. 15.The two interior opposite angles of a triangle are 32° and 43°. What is the exterior angle (in degrees)?
  16. 16.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  17. 17.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  18. 18.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  19. 19.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  20. 20.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  22. 22.Can a triangle have sides of 10 cm, 11 cm and 26 cm? (a) Yes (b) No
  23. 23.Can a triangle have sides of 9 cm, 7 cm and 9 cm? (a) No (b) Yes
  24. 24.In triangle ABC, angle A = 44° and angle B = 97°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 57° and angle B = 28°. What is angle C (in degrees)?
  26. 26.Can a triangle have sides of 8 cm, 18 cm and 8 cm? (a) Yes (b) No
  27. 27.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  28. 28.In triangle ABC, angle A = 22° and angle B = 31°. What is angle C (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest 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.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  32. 32.An exterior angle of a triangle is 120°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  34. 34.In triangle ABC, angle A = 44° and angle B = 56°. What is angle C (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 66° and 53°. What is the exterior angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  37. 37.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  38. 38.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?

Answer key

  1. 50
  2. 26
  3. 52
  4. 116
  5. 17
  6. 77
  7. 30
  8. Yes
  9. 42
  10. 112
  11. No
  12. 26
  13. 54
  14. No
  15. 75
  16. 27
  17. 5
  18. 5
  19. 17
  20. 40
  21. 5
  22. No
  23. Yes
  24. 39
  25. 95
  26. No
  27. 12
  28. 127
  29. 90
  30. 80
  31. 62
  32. 56
  33. 71
  34. 80
  35. 119
  36. 74
  37. 90
  38. 48
  39. 74
  40. 50

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