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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 460 · 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 an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  5. 5.An exterior angle of a triangle is 58°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  6. 6.Can a triangle have sides of 9 cm, 2 cm and 4 cm? (a) Yes (b) No
  7. 7.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  8. 8.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)?
  9. 9.Can a triangle have sides of 11 cm, 10 cm and 24 cm? (a) No (b) Yes
  10. 10.Can a triangle have sides of 10 cm, 4 cm and 13 cm? (a) No (b) Yes
  11. 11.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 72° each. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 86° and angle B = 63°. What is angle C (in degrees)?
  14. 14.In triangle ABC, angle A = 27° and angle B = 68°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 25° and angle B = 93°. What is angle C (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 76° and angle B = 60°. What is angle C (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  19. 19.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  21. 21.An exterior angle of a triangle is 126°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 45° and 32°. What is the exterior angle (in degrees)?
  23. 23.In triangle ABC, angle A = 40° and angle B = 85°. What is angle C (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  25. 25.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  28. 28.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  31. 31.In triangle ABC, angle A = 25° and angle B = 43°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 62° and angle B = 45°. What is angle C (in degrees)?
  33. 33.Can a triangle have sides of 12 cm, 2 cm and 16 cm? (a) Yes (b) No
  34. 34.The two interior opposite angles of a triangle are 69° and 47°. What is the exterior angle (in degrees)?
  35. 35.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  37. 37.In triangle ABC, angle A = 54° and angle B = 85°. What is angle C (in degrees)?
  38. 38.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 41° and 45°. What is the exterior angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?

Answer key

  1. 12
  2. 47
  3. 66
  4. 17
  5. 28
  6. No
  7. 18
  8. 7
  9. No
  10. Yes
  11. 54
  12. 36
  13. 31
  14. 85
  15. 62
  16. 35
  17. 44
  18. 25
  19. 72
  20. 75
  21. 78
  22. 77
  23. 55
  24. 98
  25. 27
  26. 38
  27. 10
  28. 40
  29. 120
  30. 90
  31. 112
  32. 73
  33. No
  34. 116
  35. 66
  36. 28
  37. 41
  38. 26
  39. 86
  40. 20

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