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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 548 · 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.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  2. 2.In triangle ABC, angle A = 42° and angle B = 96°. What is angle C (in degrees)?
  3. 3.Can a triangle have sides of 4 cm, 4 cm and 1 cm? (a) No (b) Yes
  4. 4.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)?
  5. 5.Can a triangle have sides of 2 cm, 12 cm and 13 cm? (a) No (b) Yes
  6. 6.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  7. 7.Can a triangle have sides of 5 cm, 2 cm and 6 cm? (a) No (b) Yes
  8. 8.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  9. 9.An exterior angle of a triangle is 142°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  11. 11.In triangle ABC, angle A = 58° and angle B = 75°. What is angle C (in degrees)?
  12. 12.Can a triangle have sides of 8 cm, 7 cm and 18 cm? (a) Yes (b) No
  13. 13.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  14. 14.Can a triangle have sides of 6 cm, 6 cm and 2 cm? (a) No (b) Yes
  15. 15.Can a triangle have sides of 2 cm, 4 cm and 3 cm? (a) Yes (b) No
  16. 16.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  19. 19.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 66° and 25°. What is the exterior angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 36° and 59°. What is the exterior angle (in degrees)?
  24. 24.In triangle ABC, angle A = 52° and angle B = 92°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 73° and 76°. What is the exterior angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 15 cm, 9 cm and 2 cm? (a) Yes (b) No
  32. 32.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  34. 34.In triangle ABC, angle A = 79° and angle B = 61°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 70° and 76°. What is the exterior angle (in degrees)?
  38. 38.Can a triangle have sides of 23 cm, 9 cm and 12 cm? (a) Yes (b) No
  39. 39.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  40. 40.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?

Answer key

  1. 100
  2. 42
  3. Yes
  4. 5
  5. Yes
  6. 25
  7. Yes
  8. 33
  9. 74
  10. 30
  11. 47
  12. No
  13. 30
  14. Yes
  15. Yes
  16. 41
  17. 66
  18. 74
  19. 32
  20. 76
  21. 91
  22. 51
  23. 95
  24. 36
  25. 51
  26. 88
  27. 39
  28. 32
  29. 149
  30. 21
  31. No
  32. 20
  33. 25
  34. 40
  35. 30
  36. 120
  37. 146
  38. No
  39. 71
  40. 48

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