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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 106 · 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 3 cm, 5 cm and 10 cm? (a) Yes (b) No
  2. 2.Can a triangle have sides of 23 cm, 11 cm and 8 cm? (a) No (b) Yes
  3. 3.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  4. 4.Can a triangle have sides of 10 cm, 25 cm and 10 cm? (a) Yes (b) No
  5. 5.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 25° and 43°. What is the exterior angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  8. 8.Can a triangle have sides of 12 cm, 2 cm and 11 cm? (a) Yes (b) No
  9. 9.In triangle ABC, angle A = 96° and angle B = 52°. What is angle C (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  12. 12.Can a triangle have sides of 4 cm, 3 cm and 8 cm? (a) No (b) Yes
  13. 13.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  17. 17.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  18. 18.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  20. 20.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)?
  21. 21.Can a triangle have sides of 6 cm, 5 cm and 8 cm? (a) Yes (b) No
  22. 22.Can a triangle have sides of 7 cm, 8 cm and 12 cm? (a) No (b) Yes
  23. 23.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  24. 24.In triangle ABC, angle A = 45° and angle B = 30°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 62° and angle B = 97°. What is angle C (in degrees)?
  26. 26.Can a triangle have sides of 6 cm, 4 cm and 7 cm? (a) No (b) Yes
  27. 27.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 25° and 51°. What is the exterior angle (in degrees)?
  30. 30.In triangle ABC, angle A = 80° and angle B = 47°. What is angle C (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  33. 33.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)?
  34. 34.In triangle ABC, angle A = 92° and angle B = 40°. What is angle C (in degrees)?
  35. 35.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  37. 37.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  38. 38.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  39. 39.In triangle ABC, angle A = 94° and angle B = 34°. What is angle C (in degrees)?
  40. 40.In triangle ABC, angle A = 38° and angle B = 89°. What is angle C (in degrees)?

Answer key

  1. No
  2. No
  3. 17
  4. No
  5. 26
  6. 68
  7. 80
  8. Yes
  9. 32
  10. 41
  11. 36
  12. No
  13. 24
  14. 40
  15. 84
  16. 108
  17. 5
  18. 17
  19. 49
  20. 15
  21. Yes
  22. Yes
  23. 34
  24. 105
  25. 21
  26. Yes
  27. 134
  28. 69
  29. 76
  30. 53
  31. 58
  32. 90
  33. 24
  34. 48
  35. 25
  36. 45
  37. 3
  38. 36
  39. 52
  40. 53

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