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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 463 · 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.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)?
  2. 2.Can a triangle have sides of 6 cm, 9 cm and 4 cm? (a) No (b) Yes
  3. 3.Can a triangle have sides of 26 cm, 9 cm and 12 cm? (a) Yes (b) No
  4. 4.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  5. 5.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  6. 6.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 49° and 52°. What is the exterior angle (in degrees)?
  8. 8.Can a triangle have sides of 5 cm, 3 cm and 5 cm? (a) No (b) Yes
  9. 9.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  15. 15.Can a triangle have sides of 8 cm, 1 cm and 8 cm? (a) No (b) Yes
  16. 16.In triangle ABC, angle A = 29° and angle B = 88°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 14 cm, 5 cm and 5 cm? (a) Yes (b) No
  19. 19.Can a triangle have sides of 12 cm, 10 cm and 22 cm? (a) Yes (b) No
  20. 20.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 8 cm, 7 cm and 8 cm? (a) Yes (b) No
  23. 23.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  25. 25.An exterior angle of a triangle is 145°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  26. 26.In triangle ABC, angle A = 55° and angle B = 46°. What is angle C (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  30. 30.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 28° and angle B = 94°. What is angle C (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  34. 34.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  36. 36.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles (in degrees)?
  38. 38.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  39. 39.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  40. 40.Can a triangle have sides of 8 cm, 23 cm and 12 cm? (a) Yes (b) No

Answer key

  1. 8
  2. Yes
  3. No
  4. 17
  5. 35
  6. 72
  7. 101
  8. Yes
  9. 26
  10. 112
  11. 75
  12. 36
  13. 27
  14. 16
  15. Yes
  16. 63
  17. 55
  18. No
  19. No
  20. 98
  21. 30
  22. Yes
  23. 64
  24. 61
  25. 69
  26. 79
  27. 11
  28. 60
  29. 65
  30. 54
  31. 68
  32. 58
  33. 13
  34. 15
  35. 30
  36. 74
  37. 30
  38. 62
  39. 36
  40. No

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