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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 320 · 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 66°. What is the third angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 9 cm, 16 cm and 6 cm? (a) Yes (b) No
  7. 7.Can a triangle have sides of 12 cm, 10 cm and 23 cm? (a) No (b) Yes
  8. 8.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 23° and angle B = 28°. What is angle C (in degrees)?
  10. 10.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  11. 11.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  14. 14.In triangle ABC, angle A = 94° and angle B = 21°. What is angle C (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 31° and 50°. What is the exterior angle (in degrees)?
  16. 16.Can a triangle have sides of 2 cm, 11 cm and 10 cm? (a) No (b) Yes
  17. 17.In an isosceles triangle, the two equal angles are 76° each. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 44° and angle B = 51°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  20. 20.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 22° and 53°. What is the exterior angle (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 158°. What is each of the other two angles (in degrees)?
  23. 23.Can a triangle have sides of 14 cm, 5 cm and 10 cm? (a) No (b) Yes
  24. 24.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 75° and 41°. What is the exterior angle (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  27. 27.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  38. 38.Can a triangle have sides of 11 cm, 11 cm and 4 cm? (a) No (b) Yes
  39. 39.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?

Answer key

  1. 24
  2. 70
  3. 72
  4. 36
  5. 27
  6. No
  7. No
  8. 78
  9. 129
  10. 90
  11. 50
  12. 72
  13. 72
  14. 65
  15. 81
  16. Yes
  17. 28
  18. 85
  19. 75
  20. 26
  21. 75
  22. 11
  23. Yes
  24. 24
  25. 116
  26. 26
  27. 18
  28. 34
  29. 21
  30. 54
  31. 32
  32. 68
  33. 72
  34. 78
  35. 40
  36. 18
  37. 46
  38. Yes
  39. 59
  40. 106

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