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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 285 · 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 triangle ABC, angle A = 29° and angle B = 40°. What is angle C (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  4. 4.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  6. 6.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  7. 7.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  8. 8.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 44° and 69°. What is the exterior angle (in degrees)?
  12. 12.In triangle ABC, angle A = 74° and angle B = 62°. What is angle C (in degrees)?
  13. 13.In triangle ABC, angle A = 74° and angle B = 83°. What is angle C (in degrees)?
  14. 14.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  15. 15.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  16. 16.In triangle ABC, angle A = 93° and angle B = 30°. What is angle C (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  18. 18.In triangle ABC, angle A = 23° and angle B = 125°. What is angle C (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  20. 20.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)?
  21. 21.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  23. 23.The two interior opposite angles of a triangle are 45° and 65°. What is the exterior angle (in degrees)?
  24. 24.In triangle ABC, angle A = 53° and angle B = 84°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 69° and angle B = 70°. What is angle C (in degrees)?
  26. 26.An exterior angle of a triangle is 127°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  27. 27.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  28. 28.Can a triangle have sides of 6 cm, 10 cm and 9 cm? (a) No (b) Yes
  29. 29.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  32. 32.In triangle ABC, angle A = 39° and angle B = 50°. What is angle C (in degrees)?
  33. 33.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?
  35. 35.Can a triangle have sides of 11 cm, 7 cm and 10 cm? (a) Yes (b) No
  36. 36.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)?
  37. 37.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  39. 39.Can a triangle have sides of 17 cm, 7 cm and 8 cm? (a) No (b) Yes
  40. 40.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?

Answer key

  1. 111
  2. 71
  3. 78
  4. 51
  5. 17
  6. 47
  7. 7
  8. 64
  9. 37
  10. 39
  11. 113
  12. 44
  13. 23
  14. 33
  15. 90
  16. 57
  17. 20
  18. 32
  19. 19
  20. 4
  21. 72
  22. 20
  23. 110
  24. 43
  25. 41
  26. 73
  27. 72
  28. Yes
  29. 32
  30. 69
  31. 30
  32. 91
  33. 40
  34. 114
  35. Yes
  36. 8
  37. 49
  38. 72
  39. No
  40. 100

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