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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 362 · 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 1 : 2 : 6. What is the smallest angle (in degrees)?
  2. 2.Can a triangle have sides of 6 cm, 12 cm and 10 cm? (a) Yes (b) No
  3. 3.The two interior opposite angles of a triangle are 75° and 60°. What is the exterior angle (in degrees)?
  4. 4.In triangle ABC, angle A = 50° and angle B = 75°. What is angle C (in degrees)?
  5. 5.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  6. 6.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  8. 8.Can a triangle have sides of 4 cm, 4 cm and 12 cm? (a) Yes (b) No
  9. 9.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 50° and 77°. What is the exterior angle (in degrees)?
  12. 12.In triangle ABC, angle A = 60° and angle B = 33°. What is angle C (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  15. 15.An exterior angle of a triangle is 55°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  16. 16.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)?
  17. 17.In triangle ABC, angle A = 69° and angle B = 67°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 54° and angle B = 36°. What is angle C (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  20. 20.Can a triangle have sides of 6 cm, 6 cm and 2 cm? (a) Yes (b) No
  21. 21.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)?
  22. 22.In triangle ABC, angle A = 26° and angle B = 131°. What is angle C (in degrees)?
  23. 23.Can a triangle have sides of 17 cm, 7 cm and 10 cm? (a) Yes (b) No
  24. 24.The two interior opposite angles of a triangle are 55° and 62°. What is the exterior angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  28. 28.In triangle ABC, angle A = 30° and angle B = 53°. What is angle C (in degrees)?
  29. 29.An exterior angle of a triangle is 72°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  31. 31.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 97° and angle B = 47°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 36° and angle B = 44°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 12 cm, 17 cm and 6 cm? (a) Yes (b) No
  35. 35.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  36. 36.Can a triangle have sides of 3 cm, 2 cm and 2 cm? (a) Yes (b) No
  37. 37.Can a triangle have sides of 8 cm, 8 cm and 3 cm? (a) No (b) Yes
  38. 38.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 24° and 23°. What is the exterior angle (in degrees)?
  40. 40.Can a triangle have sides of 10 cm, 4 cm and 18 cm? (a) Yes (b) No

Answer key

  1. 20
  2. Yes
  3. 135
  4. 55
  5. 32
  6. 15
  7. 41
  8. No
  9. 74
  10. 60
  11. 127
  12. 87
  13. 20
  14. 120
  15. 23
  16. 10
  17. 44
  18. 90
  19. 30
  20. Yes
  21. 24
  22. 23
  23. No
  24. 117
  25. 90
  26. 86
  27. 25
  28. 97
  29. 29
  30. 39
  31. 50
  32. 36
  33. 100
  34. Yes
  35. 68
  36. Yes
  37. Yes
  38. 12
  39. 47
  40. No

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