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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 52 · 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 longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  2. 2.Can a triangle have sides of 26 cm, 10 cm and 11 cm? (a) Yes (b) No
  3. 3.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  6. 6.Can a triangle have sides of 2 cm, 4 cm and 3 cm? (a) No (b) Yes
  7. 7.In triangle ABC, angle A = 57° and angle B = 72°. What is angle C (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 49° and 80°. What is the exterior angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  11. 11.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  12. 12.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  14. 14.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  15. 15.Can a triangle have sides of 7 cm, 19 cm and 10 cm? (a) Yes (b) No
  16. 16.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 33° and 47°. What is the exterior angle (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  20. 20.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  21. 21.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  23. 23.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  25. 25.Can a triangle have sides of 5 cm, 20 cm and 12 cm? (a) Yes (b) No
  26. 26.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  27. 27.The two interior opposite angles of a triangle are 60° and 66°. What is the exterior angle (in degrees)?
  28. 28.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  29. 29.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 30° and angle B = 39°. What is angle C (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 83° and angle B = 70°. What is angle C (in degrees)?
  33. 33.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  34. 34.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  35. 35.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  36. 36.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 78° and 64°. What is the exterior angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  39. 39.In triangle ABC, angle A = 29° and angle B = 106°. What is angle C (in degrees)?
  40. 40.In triangle ABC, angle A = 30° and angle B = 58°. What is angle C (in degrees)?

Answer key

  1. 24
  2. No
  3. 50
  4. 40
  5. 80
  6. Yes
  7. 51
  8. 42
  9. 129
  10. 54
  11. 29
  12. 36
  13. 26
  14. 70
  15. No
  16. 62
  17. 64
  18. 80
  19. 30
  20. 10
  21. 20
  22. 40
  23. 58
  24. 90
  25. No
  26. 5
  27. 126
  28. 4
  29. 43
  30. 111
  31. 80
  32. 27
  33. 56
  34. 26
  35. 8
  36. 45
  37. 142
  38. 71
  39. 45
  40. 92

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