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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 649 · 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 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  2. 2.In triangle ABC, angle A = 38° and angle B = 38°. What is angle C (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  4. 4.Can a triangle have sides of 11 cm, 3 cm and 12 cm? (a) No (b) Yes
  5. 5.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 12 cm, 7 cm and 12 cm? (a) No (b) Yes
  7. 7.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  8. 8.In triangle ABC, angle A = 81° and angle B = 45°. What is angle C (in degrees)?
  9. 9.Can a triangle have sides of 9 cm, 11 cm and 6 cm? (a) No (b) Yes
  10. 10.In triangle ABC, angle A = 45° and angle B = 49°. What is angle C (in degrees)?
  11. 11.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  12. 12.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)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?
  14. 14.Can a triangle have sides of 7 cm, 6 cm and 5 cm? (a) No (b) Yes
  15. 15.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 52° and 79°. What is the exterior angle (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 11 cm, 10 cm and 2 cm? (a) No (b) Yes
  20. 20.In triangle ABC, angle A = 57° and angle B = 75°. What is angle C (in degrees)?
  21. 21.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)?
  22. 22.In triangle ABC, angle A = 55° and angle B = 25°. What is angle C (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 2 cm, 10 cm and 9 cm? (a) No (b) Yes
  25. 25.An exterior angle of a triangle is 135°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  26. 26.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  27. 27.In triangle ABC, angle A = 22° and angle B = 116°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 11 cm, 20 cm and 6 cm? (a) Yes (b) No
  29. 29.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  30. 30.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  31. 31.Can a triangle have sides of 12 cm, 10 cm and 10 cm? (a) Yes (b) No
  32. 32.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  33. 33.Can a triangle have sides of 6 cm, 10 cm and 8 cm? (a) No (b) Yes
  34. 34.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  35. 35.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)?
  36. 36.Can a triangle have sides of 6 cm, 9 cm and 6 cm? (a) No (b) Yes
  37. 37.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 45° and angle B = 100°. What is angle C (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  40. 40.Can a triangle have sides of 14 cm, 8 cm and 2 cm? (a) Yes (b) No

Answer key

  1. 9
  2. 104
  3. 13
  4. Yes
  5. 74
  6. Yes
  7. 48
  8. 54
  9. Yes
  10. 86
  11. 15
  12. 24
  13. 76
  14. Yes
  15. 18
  16. 131
  17. 102
  18. 17
  19. Yes
  20. 48
  21. 15
  22. 100
  23. 25
  24. Yes
  25. 80
  26. 20
  27. 42
  28. No
  29. 57
  30. 63
  31. Yes
  32. 72
  33. Yes
  34. 48
  35. 8
  36. Yes
  37. 40
  38. 35
  39. 5
  40. No

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