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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 893 · 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 = 38° and angle B = 41°. What is angle C (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 158°. What is each of the other two angles (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  8. 8.Can a triangle have sides of 6 cm, 2 cm and 10 cm? (a) Yes (b) No
  9. 9.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  11. 11.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (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.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  15. 15.Can a triangle have sides of 5 cm, 15 cm and 8 cm? (a) No (b) Yes
  16. 16.In triangle ABC, angle A = 25° and angle B = 131°. What is angle C (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 110°. What is each of the other two angles (in degrees)?
  19. 19.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 43° and angle B = 29°. What is angle C (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  25. 25.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)?
  26. 26.Can a triangle have sides of 21 cm, 11 cm and 10 cm? (a) Yes (b) No
  27. 27.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  28. 28.In triangle ABC, angle A = 44° and angle B = 88°. What is angle C (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  30. 30.Can a triangle have sides of 7 cm, 9 cm and 4 cm? (a) No (b) Yes
  31. 31.Can a triangle have sides of 5 cm, 2 cm and 8 cm? (a) Yes (b) No
  32. 32.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  33. 33.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 8 cm, 5 cm and 8 cm? (a) No (b) Yes
  35. 35.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 38° and 57°. What is the exterior angle (in degrees)?
  37. 37.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  38. 38.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  39. 39.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?

Answer key

  1. 101
  2. 50
  3. 42
  4. 77
  5. 25
  6. 11
  7. 46
  8. No
  9. 15
  10. 42
  11. 25
  12. 70
  13. 36
  14. 50
  15. No
  16. 24
  17. 63
  18. 35
  19. 54
  20. 41
  21. 71
  22. 108
  23. 67
  24. 22
  25. 24
  26. No
  27. 64
  28. 48
  29. 17
  30. Yes
  31. No
  32. 15
  33. 27
  34. Yes
  35. 80
  36. 95
  37. 41
  38. 24
  39. 84
  40. 90

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