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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 7 · 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 longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  2. 2.The two interior opposite angles of a triangle are 54° and 74°. What is the exterior angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 41° and angle B = 71°. What is angle C (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  6. 6.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)?
  7. 7.Can a triangle have sides of 3 cm, 6 cm and 5 cm? (a) Yes (b) No
  8. 8.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  9. 9.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  10. 10.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 22° and 70°. What is the exterior angle (in degrees)?
  12. 12.Can a triangle have sides of 8 cm, 4 cm and 11 cm? (a) Yes (b) No
  13. 13.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)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  15. 15.Can a triangle have sides of 8 cm, 5 cm and 3 cm? (a) Yes (b) No
  16. 16.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 21° and angle B = 57°. What is angle C (in degrees)?
  18. 18.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  19. 19.In triangle ABC, angle A = 80° and angle B = 48°. What is angle C (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  21. 21.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)?
  22. 22.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  23. 23.Can a triangle have sides of 5 cm, 5 cm and 15 cm? (a) No (b) Yes
  24. 24.In triangle ABC, angle A = 31° and angle B = 21°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 96° and angle B = 50°. What is angle C (in degrees)?
  26. 26.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 20°. What is the third 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 triangle ABC, angle A = 52° and angle B = 75°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 41° and angle B = 33°. What is angle C (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  34. 34.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)?
  35. 35.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  37. 37.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 25° and angle B = 66°. What is angle C (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?

Answer key

  1. 24
  2. 128
  3. 27
  4. 68
  5. 53
  6. 24
  7. Yes
  8. 72
  9. 65
  10. 36
  11. 92
  12. Yes
  13. 8
  14. 10
  15. No
  16. 40
  17. 102
  18. 45
  19. 52
  20. 30
  21. 15
  22. 66
  23. No
  24. 128
  25. 34
  26. 36
  27. 70
  28. 34
  29. 53
  30. 106
  31. 100
  32. 46
  33. 38
  34. 15
  35. 38
  36. 25
  37. 30
  38. 89
  39. 36
  40. 90

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