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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 450 · 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 triangle ABC, angle A = 24° and angle B = 108°. What is angle C (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 5 cm, 9 cm and 11 cm? (a) No (b) Yes
  5. 5.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (in degrees)?
  7. 7.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)?
  8. 8.Can a triangle have sides of 11 cm, 7 cm and 13 cm? (a) Yes (b) No
  9. 9.Can a triangle have sides of 13 cm, 8 cm and 8 cm? (a) No (b) Yes
  10. 10.The two interior opposite angles of a triangle are 31° and 68°. What is the exterior angle (in degrees)?
  11. 11.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  12. 12.Can a triangle have sides of 7 cm, 13 cm and 4 cm? (a) No (b) Yes
  13. 13.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  16. 16.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  17. 17.Can a triangle have sides of 13 cm, 2 cm and 6 cm? (a) Yes (b) No
  18. 18.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  21. 21.Can a triangle have sides of 10 cm, 3 cm and 14 cm? (a) No (b) Yes
  22. 22.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 74° and angle B = 29°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 26° and angle B = 121°. What is angle C (in degrees)?
  26. 26.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  28. 28.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  30. 30.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  32. 32.Can a triangle have sides of 6 cm, 15 cm and 11 cm? (a) No (b) Yes
  33. 33.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 30° and 23°. What is the exterior angle (in degrees)?
  35. 35.In triangle ABC, angle A = 86° and angle B = 34°. What is angle C (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  37. 37.In triangle ABC, angle A = 94° and angle B = 55°. What is angle C (in degrees)?
  38. 38.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?

Answer key

  1. 48
  2. 33
  3. 61
  4. Yes
  5. 78
  6. 68
  7. 24
  8. Yes
  9. Yes
  10. 99
  11. 63
  12. No
  13. 100
  14. 114
  15. 74
  16. 25
  17. No
  18. 48
  19. 56
  20. 138
  21. No
  22. 90
  23. 50
  24. 77
  25. 33
  26. 36
  27. 32
  28. 76
  29. 25
  30. 50
  31. 69
  32. Yes
  33. 98
  34. 53
  35. 60
  36. 18
  37. 31
  38. 64
  39. 64
  40. 67

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