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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 417 · 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 12 cm, 8 cm and 21 cm? (a) Yes (b) No
  2. 2.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 45° and 38°. What is the exterior angle (in degrees)?
  6. 6.Can a triangle have sides of 17 cm, 12 cm and 3 cm? (a) No (b) Yes
  7. 7.Can a triangle have sides of 3 cm, 4 cm and 8 cm? (a) No (b) Yes
  8. 8.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)?
  9. 9.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  10. 10.In triangle ABC, angle A = 35° and angle B = 73°. What is angle C (in degrees)?
  11. 11.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  12. 12.Can a triangle have sides of 16 cm, 10 cm and 7 cm? (a) Yes (b) No
  13. 13.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  14. 14.The two interior opposite angles of a triangle are 79° and 39°. What is the exterior angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  16. 16.Can a triangle have sides of 4 cm, 6 cm and 5 cm? (a) Yes (b) No
  17. 17.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 95° and angle B = 20°. What is angle C (in degrees)?
  20. 20.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)?
  21. 21.An exterior angle of a triangle is 58°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  22. 22.In triangle ABC, angle A = 51° and angle B = 43°. What is angle C (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  24. 24.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  25. 25.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  26. 26.Can a triangle have sides of 9 cm, 11 cm and 6 cm? (a) Yes (b) No
  27. 27.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  29. 29.In triangle ABC, angle A = 73° and angle B = 25°. What is angle C (in degrees)?
  30. 30.An exterior angle of a triangle is 135°. 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 66°. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 11 cm, 10 cm and 2 cm? (a) No (b) Yes
  33. 33.In triangle ABC, angle A = 85° and angle B = 28°. What is angle C (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  37. 37.In triangle ABC, angle A = 73° and angle B = 58°. What is angle C (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  40. 40.In triangle ABC, angle A = 98° and angle B = 52°. What is angle C (in degrees)?

Answer key

  1. No
  2. 29
  3. 120
  4. 76
  5. 83
  6. No
  7. No
  8. 8
  9. 8
  10. 72
  11. 62
  12. Yes
  13. 5
  14. 118
  15. 75
  16. Yes
  17. 30
  18. 56
  19. 65
  20. 24
  21. 26
  22. 86
  23. 100
  24. 12
  25. 45
  26. Yes
  27. 66
  28. 16
  29. 82
  30. 78
  31. 24
  32. Yes
  33. 67
  34. 36
  35. 22
  36. 20
  37. 49
  38. 60
  39. 25
  40. 30

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