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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 979 · 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 14°. What is the third angle (in degrees)?
  2. 2.In triangle ABC, angle A = 23° and angle B = 61°. What is angle C (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  5. 5.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)?
  6. 6.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  7. 7.The two interior opposite angles of a triangle are 30° and 27°. What is the exterior angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  9. 9.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  10. 10.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  11. 11.Can a triangle have sides of 6 cm, 8 cm and 5 cm? (a) Yes (b) No
  12. 12.In triangle ABC, angle A = 21° and angle B = 28°. What is angle C (in degrees)?
  13. 13.In triangle ABC, angle A = 83° and angle B = 61°. What is angle C (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  15. 15.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)?
  16. 16.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 40° and 58°. What is the exterior angle (in degrees)?
  18. 18.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)?
  19. 19.An exterior angle of a triangle is 51°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  20. 20.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)?
  21. 21.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 36° and 36°. What is the exterior angle (in degrees)?
  23. 23.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  24. 24.Can a triangle have sides of 12 cm, 7 cm and 6 cm? (a) No (b) Yes
  25. 25.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  26. 26.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  27. 27.Can a triangle have sides of 4 cm, 4 cm and 12 cm? (a) Yes (b) No
  28. 28.In triangle ABC, angle A = 85° and angle B = 50°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 27° and angle B = 45°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 94° and angle B = 42°. What is angle C (in degrees)?
  31. 31.An exterior angle of a triangle is 58°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  32. 32.In triangle ABC, angle A = 71° and angle B = 70°. What is angle C (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  34. 34.In triangle ABC, angle A = 23° and angle B = 26°. What is angle C (in degrees)?
  35. 35.In triangle ABC, angle A = 37° and angle B = 107°. What is angle C (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 24° and 80°. What is the exterior angle (in degrees)?
  37. 37.Can a triangle have sides of 11 cm, 8 cm and 20 cm? (a) Yes (b) No
  38. 38.An exterior angle of a triangle is 141°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  39. 39.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?

Answer key

  1. 76
  2. 96
  3. 62
  4. 17
  5. 24
  6. 10
  7. 57
  8. 25
  9. 10
  10. 8
  11. Yes
  12. 131
  13. 36
  14. 44
  15. 24
  16. 53
  17. 98
  18. 15
  19. 31
  20. 5
  21. 72
  22. 72
  23. 16
  24. Yes
  25. 72
  26. 60
  27. No
  28. 45
  29. 108
  30. 44
  31. 30
  32. 39
  33. 36
  34. 131
  35. 36
  36. 104
  37. No
  38. 62
  39. 90
  40. 72

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