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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 604 · 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.Can a triangle have sides of 4 cm, 10 cm and 10 cm? (a) No (b) Yes
  2. 2.Can a triangle have sides of 12 cm, 9 cm and 9 cm? (a) Yes (b) No
  3. 3.Can a triangle have sides of 9 cm, 12 cm and 25 cm? (a) No (b) Yes
  4. 4.Can a triangle have sides of 8 cm, 11 cm and 6 cm? (a) No (b) Yes
  5. 5.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 12 cm, 2 cm and 9 cm? (a) No (b) Yes
  7. 7.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  9. 9.Can a triangle have sides of 2 cm, 7 cm and 9 cm? (a) Yes (b) No
  10. 10.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 69° and 51°. What is the exterior angle (in degrees)?
  13. 13.Can a triangle have sides of 11 cm, 12 cm and 2 cm? (a) Yes (b) No
  14. 14.In triangle ABC, angle A = 23° and angle B = 131°. What is angle C (in degrees)?
  15. 15.Can a triangle have sides of 6 cm, 3 cm and 8 cm? (a) No (b) Yes
  16. 16.Can a triangle have sides of 20 cm, 9 cm and 6 cm? (a) Yes (b) No
  17. 17.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 79° and angle B = 42°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 26° and angle B = 106°. What is angle C (in degrees)?
  20. 20.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  21. 21.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 8 cm, 14 cm and 2 cm? (a) Yes (b) No
  23. 23.In triangle ABC, angle A = 24° and angle B = 98°. What is angle C (in degrees)?
  24. 24.In triangle ABC, angle A = 93° and angle B = 61°. What is angle C (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  26. 26.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 64° and angle B = 69°. What is angle C (in degrees)?
  28. 28.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  29. 29.In triangle ABC, angle A = 61° and angle B = 49°. What is angle C (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 6 cm, 6 cm and 11 cm? (a) No (b) Yes
  35. 35.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 75° and angle B = 60°. What is angle C (in degrees)?
  37. 37.Can a triangle have sides of 3 cm, 10 cm and 11 cm? (a) No (b) Yes
  38. 38.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?

Answer key

  1. Yes
  2. Yes
  3. No
  4. Yes
  5. 76
  6. No
  7. 100
  8. 21
  9. No
  10. 25
  11. 66
  12. 120
  13. Yes
  14. 26
  15. Yes
  16. No
  17. 80
  18. 59
  19. 48
  20. 18
  21. 57
  22. No
  23. 58
  24. 26
  25. 17
  26. 51
  27. 47
  28. 56
  29. 70
  30. 10
  31. 55
  32. 69
  33. 71
  34. Yes
  35. 86
  36. 45
  37. Yes
  38. 66
  39. 77
  40. 18

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