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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 444 · 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 52°. What is the third angle (in degrees)?
  2. 2.In triangle ABC, angle A = 41° and angle B = 27°. What is angle C (in degrees)?
  3. 3.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  4. 4.Can a triangle have sides of 11 cm, 12 cm and 3 cm? (a) Yes (b) No
  5. 5.The two interior opposite angles of a triangle are 26° and 78°. What is the exterior angle (in degrees)?
  6. 6.Can a triangle have sides of 19 cm, 10 cm and 10 cm? (a) No (b) Yes
  7. 7.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)?
  8. 8.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  10. 10.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 9 cm, 8 cm and 6 cm? (a) No (b) Yes
  12. 12.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 60° and 41°. What is the exterior angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 51° and 50°. What is the exterior angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 44° each. What is the third angle (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  17. 17.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  18. 18.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  24. 24.The two interior opposite angles of a triangle are 56° and 31°. What is the exterior angle (in degrees)?
  25. 25.Can a triangle have sides of 2 cm, 13 cm and 11 cm? (a) Yes (b) No
  26. 26.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  27. 27.An exterior angle of a triangle is 132°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  28. 28.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)?
  29. 29.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  31. 31.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)?
  32. 32.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  33. 33.In triangle ABC, angle A = 88° and angle B = 49°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 66° and angle B = 30°. What is angle C (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  36. 36.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  39. 39.Can a triangle have sides of 8 cm, 6 cm and 8 cm? (a) Yes (b) No
  40. 40.In triangle ABC, angle A = 92° and angle B = 53°. What is angle C (in degrees)?

Answer key

  1. 38
  2. 112
  3. 72
  4. Yes
  5. 104
  6. Yes
  7. 24
  8. 70
  9. 10
  10. 26
  11. Yes
  12. 61
  13. 101
  14. 101
  15. 92
  16. 25
  17. 67
  18. 100
  19. 38
  20. 72
  21. 78
  22. 29
  23. 17
  24. 87
  25. No
  26. 36
  27. 77
  28. 16
  29. 17
  30. 71
  31. 7
  32. 30
  33. 43
  34. 84
  35. 44
  36. 40
  37. 52
  38. 63
  39. Yes
  40. 35

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