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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 337 · 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.

NameDateTime takenScore ___ / 40
  1. 1.Can a triangle have sides of 11 cm, 16 cm and 9 cm? (a) No (b) Yes
  2. 2.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  3. 3.Can a triangle have sides of 12 cm, 9 cm and 5 cm? (a) No (b) Yes
  4. 4.In triangle ABC, angle A = 96° and angle B = 46°. What is angle C (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 80° and angle B = 51°. What is angle C (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  8. 8.Can a triangle have sides of 7 cm, 9 cm and 5 cm? (a) No (b) Yes
  9. 9.In triangle ABC, angle A = 28° and angle B = 22°. What is angle C (in degrees)?
  10. 10.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 45° and 62°. What is the exterior angle (in degrees)?
  12. 12.An exterior angle of a triangle is 136°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  13. 13.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  14. 14.Can a triangle have sides of 13 cm, 9 cm and 9 cm? (a) No (b) Yes
  15. 15.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  17. 17.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)?
  18. 18.In triangle ABC, angle A = 65° and angle B = 88°. What is angle C (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  20. 20.Can a triangle have sides of 10 cm, 11 cm and 21 cm? (a) Yes (b) No
  21. 21.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  23. 23.Can a triangle have sides of 12 cm, 16 cm and 4 cm? (a) Yes (b) No
  24. 24.In triangle ABC, angle A = 73° and angle B = 23°. What is angle C (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 70° and 22°. What is the exterior angle (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 48° and angle B = 59°. What is angle C (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 13 cm, 10 cm and 4 cm? (a) No (b) Yes
  30. 30.In triangle ABC, angle A = 64° and angle B = 38°. What is angle C (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  36. 36.In triangle ABC, angle A = 59° and angle B = 81°. What is angle C (in degrees)?
  37. 37.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  38. 38.Can a triangle have sides of 15 cm, 6 cm and 10 cm? (a) No (b) Yes
  39. 39.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 54° each. What is the third angle (in degrees)?

Answer key

  1. Yes
  2. 25
  3. Yes
  4. 38
  5. 100
  6. 49
  7. 67
  8. Yes
  9. 130
  10. 29
  11. 107
  12. 58
  13. 20
  14. Yes
  15. 132
  16. 18
  17. 24
  18. 27
  19. 51
  20. No
  21. 20
  22. 26
  23. No
  24. 84
  25. 92
  26. 18
  27. 73
  28. 14
  29. Yes
  30. 78
  31. 35
  32. 27
  33. 46
  34. 90
  35. 70
  36. 40
  37. 25
  38. Yes
  39. 63
  40. 72

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