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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 796 · 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 a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  2. 2.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  4. 4.In triangle ABC, angle A = 98° and angle B = 32°. What is angle C (in degrees)?
  5. 5.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)?
  6. 6.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  7. 7.In triangle ABC, angle A = 54° and angle B = 49°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 36° and angle B = 73°. What is angle C (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  10. 10.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 33° and angle B = 72°. What is angle C (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?
  13. 13.In triangle ABC, angle A = 46° and angle B = 75°. What is angle C (in degrees)?
  14. 14.In triangle ABC, angle A = 95° and angle B = 47°. What is angle C (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  17. 17.Can a triangle have sides of 3 cm, 3 cm and 1 cm? (a) Yes (b) No
  18. 18.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 56° and angle B = 59°. What is angle C (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 3 cm, 3 cm and 6 cm? (a) No (b) Yes
  23. 23.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  25. 25.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 37° and angle B = 63°. What is angle C (in degrees)?
  27. 27.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)?
  28. 28.In triangle ABC, angle A = 77° and angle B = 68°. What is angle C (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  32. 32.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)?
  33. 33.In triangle ABC, angle A = 78° and angle B = 49°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 59° and angle B = 76°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 28° and 75°. What is the exterior angle (in degrees)?
  39. 39.An exterior angle of a triangle is 51°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  40. 40.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?

Answer key

  1. 23
  2. 42
  3. 20
  4. 50
  5. 12
  6. 50
  7. 77
  8. 71
  9. 17
  10. 102
  11. 75
  12. 54
  13. 59
  14. 38
  15. 100
  16. 21
  17. Yes
  18. 77
  19. 65
  20. 34
  21. 72
  22. No
  23. 50
  24. 77
  25. 54
  26. 80
  27. 8
  28. 35
  29. 10
  30. 75
  31. 136
  32. 24
  33. 53
  34. 45
  35. 90
  36. 122
  37. 59
  38. 103
  39. 23
  40. 8

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