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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 340 · 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 angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  3. 3.In triangle ABC, angle A = 71° and angle B = 31°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  6. 6.In triangle ABC, angle A = 22° and angle B = 84°. What is angle C (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 80° and angle B = 44°. What is angle C (in degrees)?
  12. 12.In triangle ABC, angle A = 31° and angle B = 96°. What is angle C (in degrees)?
  13. 13.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  14. 14.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  15. 15.In triangle ABC, angle A = 41° and angle B = 76°. What is angle C (in degrees)?
  16. 16.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  17. 17.In triangle ABC, angle A = 80° and angle B = 70°. What is angle C (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 53° and 29°. What is the exterior angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 36° and 52°. What is the exterior angle (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  21. 21.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  22. 22.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  24. 24.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  25. 25.In triangle ABC, angle A = 67° and angle B = 37°. What is angle C (in degrees)?
  26. 26.In triangle ABC, angle A = 31° and angle B = 46°. What is angle C (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  29. 29.Can a triangle have sides of 9 cm, 12 cm and 9 cm? (a) Yes (b) No
  30. 30.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)?
  31. 31.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 99° and angle B = 24°. What is angle C (in degrees)?
  33. 33.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  36. 36.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 65° and angle B = 48°. What is angle C (in degrees)?

Answer key

  1. 10
  2. 48
  3. 78
  4. 54
  5. 45
  6. 74
  7. 38
  8. 71
  9. 84
  10. 44
  11. 56
  12. 53
  13. 36
  14. 26
  15. 63
  16. 44
  17. 30
  18. 82
  19. 88
  20. 25
  21. 17
  22. 75
  23. 46
  24. 15
  25. 76
  26. 103
  27. 48
  28. 30
  29. Yes
  30. 7
  31. 29
  32. 57
  33. 84
  34. 62
  35. 100
  36. 63
  37. 24
  38. 72
  39. 67
  40. 67

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