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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 2 · 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 two interior opposite angles of a triangle are 52° and 36°. What is the exterior angle (in degrees)?
  2. 2.In triangle ABC, angle A = 96° and angle B = 37°. What is angle C (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  7. 7.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)?
  8. 8.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 29° and 63°. What is the exterior angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 64° and 47°. What is the exterior angle (in degrees)?
  14. 14.Can a triangle have sides of 5 cm, 4 cm and 13 cm? (a) Yes (b) No
  15. 15.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  16. 16.In triangle ABC, angle A = 49° and angle B = 66°. What is angle C (in degrees)?
  17. 17.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  18. 18.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  20. 20.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  21. 21.Can a triangle have sides of 5 cm, 9 cm and 8 cm? (a) Yes (b) No
  22. 22.Can a triangle have sides of 16 cm, 12 cm and 9 cm? (a) No (b) Yes
  23. 23.In an isosceles triangle, the two equal angles are 62° each. What is the third angle (in degrees)?
  24. 24.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 75° and angle B = 24°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 21 cm, 8 cm and 8 cm? (a) No (b) Yes
  28. 28.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  30. 30.Can a triangle have sides of 12 cm, 21 cm and 6 cm? (a) No (b) Yes
  31. 31.Can a triangle have sides of 8 cm, 21 cm and 8 cm? (a) No (b) Yes
  32. 32.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)?
  33. 33.Can a triangle have sides of 8 cm, 7 cm and 2 cm? (a) Yes (b) No
  34. 34.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 55° each. What is the third angle (in degrees)?
  36. 36.Can a triangle have sides of 8 cm, 7 cm and 15 cm? (a) No (b) Yes
  37. 37.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  38. 38.Can a triangle have sides of 9 cm, 20 cm and 9 cm? (a) No (b) Yes
  39. 39.Can a triangle have sides of 8 cm, 4 cm and 6 cm? (a) No (b) Yes
  40. 40.Can a triangle have sides of 7 cm, 19 cm and 7 cm? (a) No (b) Yes

Answer key

  1. 88
  2. 47
  3. 66
  4. 90
  5. 18
  6. 73
  7. 8
  8. 90
  9. 92
  10. 10
  11. 57
  12. 70
  13. 111
  14. No
  15. 45
  16. 65
  17. 36
  18. 39
  19. 10
  20. 68
  21. Yes
  22. Yes
  23. 56
  24. 20
  25. 140
  26. 81
  27. No
  28. 77
  29. 15
  30. No
  31. No
  32. 15
  33. Yes
  34. 42
  35. 70
  36. No
  37. 12
  38. No
  39. Yes
  40. No

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