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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 798 · 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 a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  3. 3.An exterior angle of a triangle is 131°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 70° and 20°. What is the exterior angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 32° and 30°. What is the exterior angle (in degrees)?
  6. 6.In triangle ABC, angle A = 33° and angle B = 72°. What is angle C (in degrees)?
  7. 7.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  8. 8.Can a triangle have sides of 11 cm, 24 cm and 8 cm? (a) No (b) Yes
  9. 9.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  10. 10.The two interior opposite angles of a triangle are 20° and 39°. What is the exterior angle (in degrees)?
  11. 11.In an isosceles triangle, the two equal angles are 76° each. What is the third angle (in degrees)?
  12. 12.Can a triangle have sides of 2 cm, 7 cm and 6 cm? (a) Yes (b) No
  13. 13.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 75° and 48°. What is the exterior angle (in degrees)?
  16. 16.Can a triangle have sides of 8 cm, 8 cm and 2 cm? (a) Yes (b) No
  17. 17.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  18. 18.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 93° and angle B = 47°. What is angle C (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 56° each. What is the third angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  22. 22.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)?
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 85° and angle B = 60°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 97° and angle B = 60°. What is angle C (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 75° and 49°. What is the exterior angle (in degrees)?
  29. 29.Can a triangle have sides of 2 cm, 2 cm and 1 cm? (a) Yes (b) No
  30. 30.In triangle ABC, angle A = 97° and angle B = 21°. What is angle C (in degrees)?
  31. 31.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  32. 32.In triangle ABC, angle A = 96° and angle B = 51°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 98° and angle B = 55°. What is angle C (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  35. 35.Can a triangle have sides of 8 cm, 11 cm and 18 cm? (a) Yes (b) No
  36. 36.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  37. 37.Can a triangle have sides of 11 cm, 19 cm and 9 cm? (a) Yes (b) No
  38. 38.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  39. 39.Can a triangle have sides of 6 cm, 6 cm and 3 cm? (a) No (b) Yes
  40. 40.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?

Answer key

  1. 68
  2. 40
  3. 53
  4. 90
  5. 62
  6. 75
  7. 32
  8. No
  9. 30
  10. 59
  11. 28
  12. Yes
  13. 31
  14. 50
  15. 123
  16. Yes
  17. 10
  18. 94
  19. 40
  20. 68
  21. 36
  22. 8
  23. 30
  24. 39
  25. 90
  26. 35
  27. 23
  28. 124
  29. Yes
  30. 62
  31. 70
  32. 33
  33. 27
  34. 100
  35. Yes
  36. 100
  37. Yes
  38. 57
  39. Yes
  40. 34

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