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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 878 · 40 sums
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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 triangle ABC, angle A = 38° and angle B = 95°. What is angle C (in degrees)?
  2. 2.Can a triangle have sides of 13 cm, 3 cm and 12 cm? (a) Yes (b) No
  3. 3.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  4. 4.An exterior angle of a triangle is 69°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  7. 7.In triangle ABC, angle A = 61° and angle B = 37°. What is angle C (in degrees)?
  8. 8.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  9. 9.Can a triangle have sides of 5 cm, 8 cm and 9 cm? (a) No (b) Yes
  10. 10.The two interior opposite angles of a triangle are 44° and 78°. What is the exterior angle (in degrees)?
  11. 11.Can a triangle have sides of 18 cm, 8 cm and 10 cm? (a) No (b) Yes
  12. 12.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  13. 13.Can a triangle have sides of 2 cm, 7 cm and 10 cm? (a) No (b) Yes
  14. 14.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 28° and angle B = 41°. What is angle C (in degrees)?
  18. 18.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  19. 19.In triangle ABC, angle A = 84° and angle B = 24°. What is angle C (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 44° and 69°. What is the exterior angle (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  22. 22.In triangle ABC, angle A = 98° and angle B = 34°. What is angle C (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  24. 24.In triangle ABC, angle A = 90° and angle B = 58°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 68° and angle B = 74°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 62° and angle B = 56°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 98° and angle B = 37°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 93° and angle B = 30°. What is angle C (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 75° and angle B = 70°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 80° and angle B = 73°. What is angle C (in degrees)?
  37. 37.Can a triangle have sides of 9 cm, 12 cm and 12 cm? (a) Yes (b) No
  38. 38.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (in degrees)?

Answer key

  1. 47
  2. Yes
  3. 34
  4. 35
  5. 120
  6. 74
  7. 82
  8. 24
  9. Yes
  10. 122
  11. No
  12. 27
  13. No
  14. 70
  15. 16
  16. 66
  17. 111
  18. 84
  19. 72
  20. 113
  21. 25
  22. 48
  23. 10
  24. 32
  25. 66
  26. 74
  27. 72
  28. 35
  29. 57
  30. 38
  31. 62
  32. 45
  33. 57
  34. 138
  35. 35
  36. 27
  37. Yes
  38. 90
  39. 76
  40. 68

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